WEBVTT

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So, BGP is not something that we are going to have to get heavily invested in for the Encore certification exam.

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What does that mean? It means that you are not going to have to learn all the extra nitty-gritty attributes and features and everything else that goes along with BGP.

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If you look at the exam objective, it states that you need to be able to do BGP, so eBGP I should say, configuration and verification.

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And you have to understand the BGP attributes and how it makes its decision. It's pretty much what the exam states.

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So, we are definitely going to cover that. We'll cover a little bit more, but if you are looking at getting more involved in BGP and you want to know more about iBGP and you want to know more about things like route reflectors,

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and you want to learn about some of the various communities or different attributes that go along with BGP that we won't be covering here, that's the place to go.

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Or what's the place to go? NRC. That's where you go. There you go. NRC. That's going to be the 300-410 course and certification exam.

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They will test you on a whole bunch of other things, and therefore you'll learn a whole lot more about BGP in that course.

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But we're going to stay focused here. There's still a lot we've got to learn about BGP here to get you ready for the certification exam,

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but it's more about understanding it at a high level, configure, verify, sharing routes.

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We'll talk about the BGP pass selection process and something that's not on the certification exam, the manipulation of BGP.

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There are a few things you need to know since this update of version 1.1 that's not in the exam objectives that you'll actually need to know on the certification exam.

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So, we'll have you cover there. All right. So, Board of Gateway Protocol. Primarily, it's the routing protocol of the Internet.

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That's really what it was invented for. So, it's a very, very scalable routing protocol, heavily used by ISPs, used lightly by non-ISPs.

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But what I want you to realize is that BGP is a protocol that we can use for a lot of other things.

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For example, if you've ever set up MPLS Layer 3 VPNs, BGP is being used there.

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So, maybe you formed a BGP neighborhood with your service provider.

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They're using BGP inside of their service provider environment, and then you are using BGP at the edge to connect to them at your branch office, let's say.

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So, you might be using BGP at the edge of your environment to connect to your ISP for the MPLS connection.

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And everywhere else in your organization, you might be using OSPF or EIGRP.

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So, you'll have to do a little bit of redistribution there between your OSPF and BGP or your EIGRP and BGP, whatever it is you have set up.

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You may be using BGP to connect up to your service provider for Internet connections.

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You may be doing some filtering there and a whole lot of other things that are beyond the scope of this course.

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What we need to recognize is that BGP is just a very flexible protocol that gives us an opportunity to share routes dynamically in many different types of environments.

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But for this certification exam, we're focused on enterprise-level connectivity.

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So, whether we are connecting up via MPLS or whether we are connecting up to the Internet, right, the fact of the matter is that you still have to form a BGP neighborship,

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and you'll still have to advertise the routes you want to advertise and so on and so forth.

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So, that is the gist of ENCQOR, making sure that you understand the basis of BGP.

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So, no matter what type of environment you want to use it in, whether it's for MPLS or whether it's for Internet connectivity,

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then you have the fundamental knowledge that you need in order to be successful with that.

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So, the primary thing you have to recognize is that BGP has the concept of autonomous systems.

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Now, in a previous session, many of you had indicated that you were using EIGRP.

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And for those of you using EIGRP, when you set up EIGRP, you have to specify an autonomous system that EIGRP is going to be running in.

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Well, this is not the same thing, right?

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This is not the same thing, right?

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When we use autonomous systems for EIGRP, that is locally significant to us, even though we might be using the same numbering system as BGP.

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But an EIGRP autonomous system is locally significant to us, and it would be a collection of routers that are enabled to share EIGRP information with each other.

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So, if I have a router running EIGRP and I configure it to be an EIGRP autonomous system 100,

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then any other router I want it to share routes with are also going to have to be an EIGRP autonomous system 100.

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All right, but when it comes to BGP, when we're dealing with autonomous systems, we are referring to a collection of networks,

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a collection of IPv4 or IPv6 networks along with their routers, the collection of routers that go along with that under the control of a single organization.

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So, every single environment, every single entity that wants to use BGP and be part of the Internet using BGP is going to have to have an autonomous system number,

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because that autonomous system number represents you out on the Internet.

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And that autonomous system number is going to be associated with all of those public IP addresses, IPv4 and IPv6 addresses that are addressed to you.

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So, therefore, autonomous system numbers have to be unique, just like IPv4 and IPv6 addressing.

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And this is one of the most important aspects of BGP.

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BGP heavily relies on these autonomous system numbers for many different reasons, and one of them is routing.

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Routing, and you'll see that here momentarily.

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So, when you think about this group right here, autonomous system 65,250, let's pretend that's you.

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And let's pretend this is me.

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If we wanted to share public information with each other, we could run BGP.

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And the end result is that what I am sharing using BGP, you will ultimately learn using BGP.

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So, if you change this, there's you, and there's your ISP as an example.

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So, whether this is an Internet connection you have or whether it's an MPLS connection you have, it doesn't matter.

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In the end, you are going to form a BGP session with your what?

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With your Internet service provider.

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And then whatever IP networks you have, a public IPv4 network, public IPv6 networks you have that you want to, let's say, exchange, so that's for the Internet example,

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then you can exchange that using BGP with your ISP, and then they can share that to everyone else.

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And if you were using something like MPLS instead, the whole point of MPLS is that over here, you'd, let's say, have your branch office.

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That's your branch office, and let's say this is your headquarters.

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So, in this case, if this is your headquarters and that's your branch office, and we're running MPLS, so this is not the Internet anymore, right?

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It's a private network hosted by the service provider.

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What's going to happen now is you use BGP, so that way there you can take that IPv6 network,

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and then redistribute them into BGP, so that way there they can be taken over the MPLS network and sent over to your branch office, and vice versa.

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And then you can route between your branch office and your headquarters environment over that.

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So, you can see how with BGP, we have many different ways that we can implement it, depending on the scenario and circumstances,

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but these autonomous system numbers, especially for the Internet, are really, really important,

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because these autonomous system numbers are really, really important.

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But these autonomous system numbers, especially for the Internet, are really, really important,

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because the autonomous system numbers for the Internet are going to make sure that we are all unique and identifiable out on the Internet.

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So, we look here at my crude diagram of the Internet.

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What do we have? Well, we have you over here.

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Let's say this is me over here. Let's say this is Cisco over here.

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You have an autonomous system number. Let's just throw in 65,238.

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So, you are here. So, your ISPs, you've got dual ISP connectivity.

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Those are your ISPs, and you've got other ISPs, and you've got Cisco over here.

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Cisco just happens to be my ISP.

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Not really, but, you know, the idea here is for you to recognize how we're all interconnected together.

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We've got this web of autonomous systems, and inside each of these autonomous systems are what?

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Public networks, public servers, public services, public resources that we can access,

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as well as private resources that we're not allowed to access.

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So, in the end, for example, let's say this is Cisco's public IP, 192.0.0.24.

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What public network do they have? An autonomous system, 1024.

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So, if we looked up, for example, autonomous system 1024, then we would see Cisco's addresses in there.

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Now, that's not really Cisco's autonomous system number.

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But if you want to look up autonomous system numbers, you can absolutely do so.

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That's public knowledge, folks.

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So, you can just do a Google search. Who owns autonomous system or this?

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What IP addresses are part of autonomous system or that?

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You can get all that information.

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That's not secretive information. That's public information.

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But the idea here is that you, using BGP, can learn about that specific public network.

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Just like inside of your organization using OSPF or EIGRP,

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you can learn about those specific private networks inside your organization.

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So, with BGP, though, it's not like OSPF.

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BGP is more like EIGRP, sort of.

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Why? Distance vector. This is a path vector protocol.

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What does that mean?

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It means I know, for example, about this network because I own it.

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I own it.

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So, what do I do? I share it.

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I share it with all my BGP neighbors.

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So, I share it with these other autonomous systems that are beyond my control.

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And then each one of these autonomous systems have to ultimately figure out

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what is the best, most efficient, most effective way for me to get to that particular network.

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And once it makes that decision, it can then tell all of its neighbors the decision it has made.

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So, if you focus on this network down here, for example, let's say it decides we're going this way.

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Then what's it going to do? It's going to tell this autonomous system that.

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It's going to tell this autonomous system that.

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But it will not tell the autonomous system that taught it.

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Why? Because that is what we call the split horizon rule.

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And with BGP, the split horizon rule is making sure that you don't share information back to the source that actually gave it to you.

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So, if this autonomous system is giving me that information, then I don't share that information back with them.

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Because that could cause a routing loop.

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So, it's a split horizon rule.

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So, now when you look at my autonomous system here, I've learned from two different ways now.

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I learned from this autonomous system.

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I learned from this autonomous system.

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So, in this case, let's say I choose to go this way because that's the quicker way to go.

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Well, then I'll share with this router that I have about that.

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But now, not router, autonomous system.

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Now, this autonomous system has already chosen this way.

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And when it receives the information from me, let's say it's like, oh, that's not good enough.

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Okay, well, it's just going to keep it.

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It's going to keep it as alternative path.

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But it's not going to use it.

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It's going to keep using this path right here.

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So, every time that autonomous system is learning about a network, it's going to have to compare that to what it already knows.

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And if that information is better, then it's going to use it.

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If it's not better, then it's going to just store it for later, potentially, if it needs it.

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So, as we continue this ripple effect through the internet, eventually, you learn about it from here, and you learn about it from here.

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Now, you have to make a decision.

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Which way are you going to go to get to 192.02.024, autonomous system 1024?

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And let's say you choose to go this way.

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This is the way you choose to go.

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So, you will no longer go this way, but you'll keep that information for later use, and you'll send all your traffic this way.

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Now, this autonomous system, which way is it going?

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Well, you don't know that, right?

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You don't necessarily know that.

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Now, you can find out that information, or you can look up information, and you can verify paths and stuff like that through the internet.

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But in the end, let's say it decided to go this way, and this autonomous system decided to go this way.

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That's pretty efficient in this particular example.

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This path is pretty efficient.

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But there are times in the world of BGP where the path that is chosen is not the most efficient path.

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And the reason why is because there is no way for BGP to know the number of routers in each autonomous system, the number of links in each autonomous system, the number or the amount of delay or congestion that is happening in a particular autonomous system.

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So, having the ability to monitor over time mission-critical paths that you may have is important because you might need to tweak your decision-making process.

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Maybe it's better to go this way, right?

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If there is 10,000 routers in each of these autonomous systems that traffic had to go through, but up here there's only five in each, maybe this is a better way to go.

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Even though it's longer, hop-wise, autonomous system-wise, maybe it's a better way to go.

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So, you're not going to have to manipulate any of that per se on the certification exam, but it's just to give you an idea that you're playing this big giant sandbox with a whole bunch of kids and everybody's got to play fairly here.

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And everybody's going to be different.

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And we'd still have to get along in this big old giant internet of autonomous systems that we have.

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So, you're going to need an autonomous system if you plan on playing on the internet.

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But you don't necessarily need one.

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For example, I'll get into that momentarily.

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But when you need a public autonomous system, you can reach out to your ISP or your regional registry to get a public autonomous system number.

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So, autonomous system numbers are created and assigned by the Internet Assigned Numbers Authority through regional registries or ISPs.

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So, if you go to your ISP, then you're essentially going to be getting an autonomous system number from the ISP that was given to them.

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And it's going to be tied to that ISP, though, meaning that if you choose to leave that ISP and go somewhere else, you have to give up that autonomous system number.

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But if you go to a regional registry, then you are going to be able to get an autonomous system that's not tied to any ISP.

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And you're going to be able to bring that autonomous system number with you to any ISP that you go to.

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So, there's pros and cons to each, right?

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If you get it from a regional registry, it's more likely going to cost you a lot more money than just getting it directly from your ISP.

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So, you'll have to research that and figure out what's better for us.

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Typically, if you're a dual home to two different ISPs, so if this is ISP 1 and this is ISP 2, and you're dual home connected to them, so this is you, then typically it's better to go with a regional registry.

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So, that way your autonomous system number is not tied to any individual ISP.

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That way I can use that autonomous system number to represent me and connect up to both of those different ISPs.

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So, our range originally was from 1 to 65,535, or essentially zero, all right, 65,535.

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We could use 1 to 64,511 as public.

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And then for private, we could use this range right here.

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So, what does private mean?

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Private means you can go ahead and use those without jeopardizing the internet.

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It's like your RFC 1918 addresses for IPv4.

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So, that way there, if you wanted to set up IPv4 addressing in your environment, use your private RFC 1918 addresses, and that doesn't conflict with anybody else who's using any other address on the internet or even in their own environment because of the way we use them and set them up.

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So, same thing with these private autonomous system numbers.

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When you use them, you're not going to be hurting the internet.

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Now, when you think about what I've just described to you, I said that every single organization essentially needs an autonomous system number if they're going to be playing on the internet.

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So, this ran out pretty fast, as you can imagine, through the 90s internet explosion.

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So, it wasn't long after that where they had to expand that range from 65,536 all the way up to, actually the end number is right here, 4.2, that's 3, 3, 3, 3, 4.2 billion is what we have in total now.

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So, there's your public range going from here to here, and then from here to here, and then your private range going from here to here, and then from here to here.

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So, any of those numbers in the public range can be used for internet, and anything in the private range can be used for just goofing around in your own environment, setting up demo labs, different things like that if you want to.

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However, you can use private on the internet, sort of.

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Now, why do I say it that way?

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Because there are times when it doesn't make sense for you to spend the money on autonomous system number when it's not really going to make a difference.

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Maybe if you're a small or medium organization, you don't really need your own autonomous system number, and you just have a few public IP addresses.

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What you can do is you can still use BGP with your service provider.

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So, let's say this is you.

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Let's use a private autonomous system number like 65,534.

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And you're connected up to your ISP, and let's say your ISP is autonomous system number nine, and then this is the rest of the internet.

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So, and you have some public IP, like let's say you had 192.0.1.0.24, and you owned 192.0.2.0.24.

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Those are your public IPs that were actually given to you by your ISP, and you're using those inside of your environment.

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But you want to advertise those out to the internet, so that way their users out on the internet can access those public resources that you have in those subnets.

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What your ISP can do is they can actually strip your autonomous system number, meaning that you have an agreement with them.

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Instead of paying for an autonomous system number, you're going to piggyback on top of their autonomous system number, essentially.

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So, when you go ahead and you advertise your networks, you're going to be advertising your networks as 192.0.1.0.24 via autonomous system number 65,534, and 192.0.2.0.24 via autonomous system number 65,534.

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Now, when your ISP gets that, because of your agreement you have with them, and they know what they've got to do, they've configured their routers, they've configured to strip your autonomous system number.

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So, now when they advertise it out, it's going to be 192.0.1.0.24 via autonomous system number 9.

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192.0.2.0.24 via autonomous system 9.

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Okay, so they stripped it out.

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Now, if you're using a public autonomous system number, let's change that to a public one.

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Let's say you're using public autonomous system number 45.

00:20:27.000 --> 00:20:29.000
Well, how does that change things?

00:20:30.000 --> 00:20:36.000
Well, I would be advertising to my service provider autonomous system number 45 for both of these.

00:20:37.000 --> 00:20:47.000
And then, when they advertise it out to the rest of the world, they just add to the list 45,9.

00:20:48.000 --> 00:20:50.000
45,9 as you can see.

00:20:51.000 --> 00:20:53.000
So, that list grows and grows and grows, that autonomous system number list.

00:20:53.000 --> 00:20:57.000
So, when we go back to this example now, they understand autonomous system numbers better.

00:20:58.000 --> 00:21:17.000
When you think about you, you are going to see 192.0.2.0.24 via 65,000, let me clean this up, 65,431, 6021, 1024 when it's all said and done.

00:21:18.000 --> 00:21:21.000
Let's go to a BGP router out on the internet.

00:21:21.000 --> 00:21:28.000
When we connect to this BGP router that's on the internet, if we type in show IP BGP, we'll look at the BGP table.

00:21:29.000 --> 00:21:34.000
What I want you to see is the autonomous system path right here as listed.

00:21:35.000 --> 00:21:46.000
So, you'll see that the network 1.0.0.0.24, this router has learned from this neighbor, this one, this one, this one, this one, this one, this one, this one, this one, this one, this one, this one, this one, this one, all of these, all right?

00:21:47.000 --> 00:21:52.000
And if you look, the autonomous system number at the very end is the exact same.

00:21:53.000 --> 00:21:55.000
It's the exact same for all of these.

00:21:56.000 --> 00:22:03.000
So, under path, you'll see this one has 2, 2, 2, 2, 2, this one has 3 paths or 3, not 3 paths, 3 autonomous systems.

00:22:04.000 --> 00:22:08.000
This one has 4, this one has 5 in order to get there, right?

00:22:09.000 --> 00:22:12.000
So, when you look at those, the last one's always the same.

00:22:12.000 --> 00:22:13.000
Why?

00:22:13.000 --> 00:22:16.000
Because this autonomous system owns this network.

00:22:17.000 --> 00:22:23.000
If we go down to this one down here, 1.0.4.0.24, who owns that?

00:22:24.000 --> 00:22:31.000
Autonomous system number 38803, 38803, 38803, and so on and so forth, right?

00:22:32.000 --> 00:22:40.000
So, we can see here that the path we could possibly take in these different scenarios, for example, from this router right here,

00:22:40.000 --> 00:22:46.000
whatever autonomous system they live in, they would then have to go to this autonomous system,

00:22:47.000 --> 00:22:54.000
then this autonomous system to ultimately get to the destination autonomous system that owns that particular network.

00:23:02.000 --> 00:23:07.000
Anybody know how many approximate networks there are on the IPv4 Internet right now?

00:23:08.000 --> 00:23:09.000
There it is.

00:23:10.000 --> 00:23:15.000
This router knows 985,336 public networks.

00:23:19.000 --> 00:23:27.000
And it has learned about them from the following BGP neighbors, BGP neighbors that it has.

00:23:28.000 --> 00:23:34.000
So, this router's connected to a lot of different neighbors, a lot of different autonomous systems it's connected to.

00:23:34.000 --> 00:23:41.000
And you'll see it's learned this many from that neighbor, this many from that neighbor, this many from that neighbor, this many from that neighbor.

00:23:42.000 --> 00:23:43.000
That's a lot.

00:23:43.000 --> 00:23:54.000
So, in total, it's learned this many different options, 1.8 million, no, 18 million, I should say, different options.

00:23:55.000 --> 00:23:59.000
But there's only 985 unique of them within that 18 million.

00:23:59.000 --> 00:24:03.000
So, just imagine what type of router you need to be able to accomplish something like this.

00:24:04.000 --> 00:24:06.000
I'm going to type in show IP route.

00:24:06.000 --> 00:24:10.000
And remember what we said, there's how many?

00:24:10.000 --> 00:24:12.000
985,000.

00:24:12.000 --> 00:24:15.000
So, the BGP routing table on this router.

00:24:18.000 --> 00:24:20.000
We'd be here all day, all day.

00:24:21.000 --> 00:24:24.000
Because every time I hit spacebar, it shows 24 at a time.

00:24:25.000 --> 00:24:32.000
Because every time I hit spacebar, it shows 24 at a time, which is 985,000 times 24, or divided by 24.

00:24:32.000 --> 00:24:34.000
That's how many times I have to hit spacebar.

00:24:36.000 --> 00:24:37.000
Anyways, there you go, folks.

00:24:37.000 --> 00:24:39.000
There is an example of BGP.

00:24:39.000 --> 00:24:41.000
We'll come back to that, and we'll show you.

00:24:41.000 --> 00:24:42.000
We'll use that.

00:24:42.000 --> 00:24:51.000
We'll use that router to learn about the attributes later, because we can see all the attributes, and there's a lot of good information in there that we can use from a learning standpoint today.

00:24:51.000 --> 00:24:59.000
But we're going to play around in our live environment today as we configure BGP and teach you that, because I'm not allowed to configure BGP on those routers.

00:24:59.000 --> 00:25:01.000
The router doesn't belong to me.

00:25:01.000 --> 00:25:02.000
All right, so BGP basics.

00:25:02.000 --> 00:25:06.000
Things to always remember about BGP is that it's not its own transport protocol.

00:25:06.000 --> 00:25:10.000
Okay, so EIGRP is its own transport protocol.

00:25:10.000 --> 00:25:13.000
OSPF is its own transport protocol.

00:25:13.000 --> 00:25:16.000
We said OSPF is protocol number 89.

00:25:16.000 --> 00:25:18.000
EIGRP is protocol number 88.

00:25:18.000 --> 00:25:20.000
Well, BGP actually uses TCP.

00:25:21.000 --> 00:25:23.000
TCP port 179.

00:25:23.000 --> 00:25:30.000
So, folks, with EIGRP, you have to be directly connected to form a neighbor adjacency with each other.

00:25:30.000 --> 00:25:33.000
You have to be in the same subnet, same broadcast domain.

00:25:33.000 --> 00:25:35.000
Same thing is true with OSPF.

00:25:35.000 --> 00:25:38.000
In order to form a neighbor adjacency, you have to be in the same what?

00:25:38.000 --> 00:25:39.000
Subnet, right?

00:25:39.000 --> 00:25:40.000
Same broadcast domain.

00:25:40.000 --> 00:25:41.000
And we're using what?

00:25:41.000 --> 00:25:43.000
Multicast addressing.

00:25:43.000 --> 00:25:46.000
224005 and 6 for OSPF.

00:25:46.000 --> 00:25:50.000
2240010 for EIGRP.

00:25:50.000 --> 00:25:52.000
Okay, with BGP, we're using TCP.

00:25:52.000 --> 00:26:01.000
So does that mean that I have to be directly connected to form a neighbor adjacency if we're using TCP?

00:26:01.000 --> 00:26:11.000
Yes or no, what do you think?

00:26:11.000 --> 00:26:12.000
No, we don't have to.

00:26:12.000 --> 00:26:14.000
We don't have to.

00:26:14.000 --> 00:26:21.000
So, for example, if I wanted to form a BGP neighborhood from here over to here, I can do that.

00:26:21.000 --> 00:26:27.000
I form a BGP neighborhood from here all the way over to here.

00:26:27.000 --> 00:26:28.000
Why?

00:26:28.000 --> 00:26:29.000
TCP.

00:26:29.000 --> 00:26:37.000
So as long as I know how to get to you and I know your IP address and you know my IP address and my information,

00:26:37.000 --> 00:26:40.000
you can get to me, we can form a BGP neighborhood with each other.

00:26:40.000 --> 00:26:45.000
Now, by default, they force you to be directly connected together in the same subnet, right?

00:26:45.000 --> 00:26:50.000
By default, with EBGP, they force you to be directly connected.

00:26:50.000 --> 00:27:04.000
But you can override that by just changing the number of hops away up to a maximum of 255 in order to form a BGP neighborhood.

00:27:04.000 --> 00:27:06.000
So TCP, TCP.

00:27:06.000 --> 00:27:12.000
So as long as I can form a TCP session with you, then I can form a BGP neighborhood with you.

00:27:12.000 --> 00:27:19.000
And because we're using TCP and we're going to be using port numbers here, it's basically client-server now in this case.

00:27:19.000 --> 00:27:24.000
One device is going to be the server, and the server uses port 179.

00:27:24.000 --> 00:27:28.000
And the other one is going to be the client, and it's going to use an ephemeral port number.

00:27:28.000 --> 00:27:29.000
Ephemeral port numbers are what?

00:27:29.000 --> 00:27:33.000
Approximately $42,000 up to $65,535, right?

00:27:33.000 --> 00:27:39.000
So let's say this device is initiating the session.

00:27:39.000 --> 00:27:44.000
If it initiates the session, it's typically going to be the client in that particular case.

00:27:44.000 --> 00:27:48.000
So let's say I pick port number 55,389.

00:27:48.000 --> 00:27:56.000
And therefore, this is the one that's going to be responding to my initiation, so it's typically going to be the server 179.

00:27:56.000 --> 00:27:59.000
So think about access control lists along this path.

00:27:59.000 --> 00:28:06.000
It's going to be important to make sure that there's no ACL in between that's blocking the ability to form this TCP session.

00:28:06.000 --> 00:28:12.000
Now, typically what happens, though, is both routers try to form a TCP session because when we configure our devices,

00:28:12.000 --> 00:28:15.000
they both try to become the clients right away.

00:28:15.000 --> 00:28:17.000
So they both try to become the clients.

00:28:17.000 --> 00:28:22.000
Let's say I pick 49,284, TCP port 179.

00:28:22.000 --> 00:28:26.000
The problem is you can't have two TCP sessions for your BGP.

00:28:26.000 --> 00:28:27.000
So great news.

00:28:27.000 --> 00:28:29.000
It just automatically solves this problem for you.

00:28:29.000 --> 00:28:34.000
What it does is it goes ahead and does its thing and then realizes, oops, we have two sessions,

00:28:34.000 --> 00:28:36.000
and then it'll tear down one of those sessions.

00:28:36.000 --> 00:28:40.000
Typically, the one with the higher router ID will remain the server,

00:28:40.000 --> 00:28:44.000
and then the other one with the lower router ID will remain the client.

00:28:44.000 --> 00:28:46.000
So no big deal there.

00:28:46.000 --> 00:28:48.000
But you could control who's the client if you want to.

00:28:48.000 --> 00:28:50.000
You can control who the server is.

00:28:51.000 --> 00:28:55.000
But the only time you would ever need to do that would be in a scenario where,

00:28:55.000 --> 00:29:04.000
let's say there was an access control list in between and the ACL was blocking TCP port 179 this way as a destination.

00:29:04.000 --> 00:29:07.000
Well, then that would mean you would have no choice but to make sure this one's the client

00:29:07.000 --> 00:29:09.000
and this one's the server in order for this to work out.

00:29:09.000 --> 00:29:10.000
But here's the deal.

00:29:10.000 --> 00:29:15.000
If there was an ACL blocking it that way, then as soon as this client works,

00:29:15.000 --> 00:29:17.000
then it's all going to work itself out anyways.

00:29:17.000 --> 00:29:19.000
There's not really anything you have to do.

00:29:19.000 --> 00:29:25.000
But you can purposely force with certain commands on your device exactly which one's server and which one's client.

00:29:25.000 --> 00:29:29.000
But not a big deal typically.

00:29:29.000 --> 00:29:30.000
Path vector.

00:29:30.000 --> 00:29:34.000
So it's distance vector-based, as you've already seen with the autonomous systems.

00:29:34.000 --> 00:29:38.000
We are going to be taking information that we learned via BGP,

00:29:38.000 --> 00:29:42.000
making a decision about that, and then sharing with all other autonomous systems that are connected to us.

00:29:42.000 --> 00:29:44.000
Now as I'm saying autonomous systems, I'm not saying routers,

00:29:44.000 --> 00:29:48.000
because you can have 50 routers inside of your autonomous system all running BGP.

00:29:48.000 --> 00:29:51.000
And, yes, all those routers will potentially learn about all the information,

00:29:51.000 --> 00:29:55.000
but this is really about training autonomous systems about another autonomous system,

00:29:55.000 --> 00:29:57.000
about another autonomous system, about another autonomous system.

00:29:57.000 --> 00:30:00.000
It's not about just training routers.

00:30:00.000 --> 00:30:03.000
It's training all the routers inside of an autonomous system.

00:30:03.000 --> 00:30:07.000
So this is a path vector protocol similar to distance vector,

00:30:07.000 --> 00:30:09.000
but it's not going to be router-by-router basis.

00:30:09.000 --> 00:30:14.000
It's more about autonomous system-by-autonomous system basis.

00:30:14.000 --> 00:30:19.000
We are forming neighbor adjacencies, but one of the things I want you to realize is that these are static.

00:30:19.000 --> 00:30:20.000
Static, not dynamic.

00:30:20.000 --> 00:30:23.000
With OSPF and EIGRP, we did what?

00:30:23.000 --> 00:30:24.000
We did dynamic.

00:30:24.000 --> 00:30:27.000
I enabled the routing process on the interface, and when that happens, what occurs?

00:30:27.000 --> 00:30:34.000
We send out multicast packets, 224.0.0.5, with EIGRP, 224.0.0.10, and what happens?

00:30:34.000 --> 00:30:38.000
We automatically form neighbor adjacencies with other routers participating in EIGRP or OSPF.

00:30:38.000 --> 00:30:43.000
Okay, with BGP, I have to statically define exactly the parameters for that neighborhood.

00:30:43.000 --> 00:30:44.000
I have to type in your IP address.

00:30:44.000 --> 00:30:46.000
You have to type in my IP address.

00:30:46.000 --> 00:30:48.000
I have to type in your autonomous system number.

00:30:48.000 --> 00:30:50.000
You have to type in my autonomous system number.

00:30:50.000 --> 00:30:51.000
That's how we find each other.

00:30:51.000 --> 00:30:55.000
There is no dynamic neighborhood here.

00:30:55.000 --> 00:30:59.000
Now, beyond the scope of this course and exam, there is an option for dynamic neighborhood,

00:30:59.000 --> 00:31:04.000
but it boils down to you just telling your router, hey, if another router reaches out to you to form a BGP neighborhood,

00:31:04.000 --> 00:31:06.000
go ahead and form a neighborhood with them.

00:31:06.000 --> 00:31:11.000
That's what it means to be dynamic in BGP, but typically you're going to do static neighborhood adjacencies.

00:31:11.000 --> 00:31:16.000
You're not going to just let your router just form a neighborhood with anybody who asks it to become a neighbor.

00:31:16.000 --> 00:31:18.000
And then once we're neighbors, what do we do?

00:31:18.000 --> 00:31:21.000
We advertise network layer reachability information.

00:31:21.000 --> 00:31:24.000
Let me repeat that, network layer reachability information.

00:31:24.000 --> 00:31:28.000
So in the world of BGP, we call it NLRIs, network layer reachability information.

00:31:28.000 --> 00:31:36.000
It's just a fancy way to say things like the network ID, the subnet mask, and all of the attributes that go along with it.

00:31:36.000 --> 00:31:44.000
So, for example, ooh, network 192.0.2.0.24, and then all the attributes that go along with it,

00:31:44.000 --> 00:31:51.000
things like the MED, the autonomous system path, the weight, the local, and anything else we can, communities, et cetera, et cetera,

00:31:51.000 --> 00:31:55.000
and the list goes on, lots and lots of attributes for BGP.

00:31:55.000 --> 00:31:59.000
Now, the exam objectives stipulate that you need to understand eBGP,

00:31:59.000 --> 00:32:02.000
but I'm also going to cover a little bit of iBGP here for you today,

00:32:02.000 --> 00:32:06.000
because that way there, you have a better chance of understanding the scenarios and situations on the exam,

00:32:06.000 --> 00:32:09.000
because the last thing I want is for you to only learn about eBGP,

00:32:09.000 --> 00:32:14.000
and then on the exam, for some reason, they throw iBGP on it, even though it's not part of the exam objectives.

00:32:14.000 --> 00:32:16.000
And if they do that, I don't want you to be confused.

00:32:16.000 --> 00:32:21.000
I want you to be able to clearly identify one from the other and accomplish the objectives of the certification exam.

00:32:21.000 --> 00:32:23.000
So let's start off with eBGP here.

00:32:23.000 --> 00:32:28.000
eBGP simply means you're peering between routers and different autonomous systems,

00:32:28.000 --> 00:32:31.000
and by default, they have to be directly connected.

00:32:31.000 --> 00:32:33.000
So I've already typed in directly connected here,

00:32:33.000 --> 00:32:37.000
meaning you're going to have to be in the same subnet in order to form your neighborship.

00:32:37.000 --> 00:32:48.000
So, for example, if this is me right here, and this is my ISP right here,

00:32:48.000 --> 00:32:57.000
so I'm going to go ahead and I'm going to form an eBGP session with my ISP.

00:32:57.000 --> 00:33:00.000
Typically, we're going to be in the same subnet in this case.

00:33:00.000 --> 00:33:07.000
We're directly connected in this case, because if I go to this interface,

00:33:07.000 --> 00:33:12.000
it might be 203.0113.89 slash 29 as an example.

00:33:12.000 --> 00:33:18.000
Over here, it's 203.0113.91, let's say, slash 29.

00:33:18.000 --> 00:33:20.000
So we are directly connected.

00:33:20.000 --> 00:33:22.000
We are in the same subnet.

00:33:22.000 --> 00:33:26.000
So when we say directly connected, we mean from the perspective of Layer 3 IP addressing,

00:33:26.000 --> 00:33:30.000
not Layer 1 as an example in this case.

00:33:30.000 --> 00:33:34.000
And the same thing is true with OSPF and EIGRP, directly connected in the same subnet,

00:33:34.000 --> 00:33:36.000
not directly connected at Layer 1 as an example.

00:33:36.000 --> 00:33:40.000
Because if I had a router and a switch, and I had five routers all connected to that same switch,

00:33:40.000 --> 00:33:42.000
we're not technically directly connected, are we?

00:33:42.000 --> 00:33:46.000
No, we're all directly connected to the switch, but we're all in the same Layer 3 network.

00:33:46.000 --> 00:33:52.000
That's what they mean by directly connected, making sure that we're one hop away from each other.

00:33:52.000 --> 00:33:55.000
So if I leave this interface within one hop, I'm at you.

00:33:55.000 --> 00:33:58.000
That's what it boils down to.

00:33:58.000 --> 00:34:03.000
So with eBGP, by default, you can't route an eBGP packet.

00:34:03.000 --> 00:34:05.000
You can't route an eBGP packet.

00:34:05.000 --> 00:34:10.000
If I take it from here and I send it out, the next router has to be the neighboring device.

00:34:10.000 --> 00:34:13.000
But like I said, you can change that behavior.

00:34:13.000 --> 00:34:19.000
So that way there, you could be up to 255 hops away.

00:34:19.000 --> 00:34:23.000
And by doing so, then I could technically form, if I wanted to form a neighborhood from here

00:34:23.000 --> 00:34:32.000
all the way over to this router, we absolutely could just by changing that parameter from one hop default

00:34:32.000 --> 00:34:36.000
to whatever many hops we want to allow.

00:34:36.000 --> 00:34:38.000
Right now, iBGP is about what?

00:34:38.000 --> 00:34:42.000
Peering with any router inside of the same autonomous system.

00:34:42.000 --> 00:34:46.000
So, for example, when you look at all these routers here, they're in my autonomous system.

00:34:46.000 --> 00:34:51.000
If I set up BGP on this router and I set up BGP on this router, then they're in the same autonomous system.

00:34:51.000 --> 00:34:55.000
That's called an iBGP peering, interior border gateway protocol.

00:34:55.000 --> 00:35:01.000
And in this case, you can be up to automatically, by default, 255 hops away.

00:35:01.000 --> 00:35:05.000
255 hops away.

00:35:05.000 --> 00:35:06.000
So what does that mean?

00:35:06.000 --> 00:35:08.000
It means you don't have to be directly connected to each other.

00:35:08.000 --> 00:35:10.000
So take a peek at this router.

00:35:10.000 --> 00:35:12.000
Take a peek at this router.

00:35:12.000 --> 00:35:15.000
They are not connected together at all.

00:35:15.000 --> 00:35:16.000
There's an arrow there, right?

00:35:16.000 --> 00:35:17.000
There's an arrow.

00:35:17.000 --> 00:35:19.000
But there's no line between them.

00:35:19.000 --> 00:35:21.000
Okay, there's no line between them.

00:35:21.000 --> 00:35:25.000
Yeah, we can still form an iBGP peering with each other.

00:35:25.000 --> 00:35:31.000
So that way we can share BGP information with each other.

00:35:31.000 --> 00:35:33.000
TCP, the powers of TCP.

00:35:33.000 --> 00:35:34.000
All right.

00:35:34.000 --> 00:35:37.000
So what we're going to do here today is we're going to set up BGP.

00:35:37.000 --> 00:35:41.000
We're going to do eBGP from here up to here.

00:35:41.000 --> 00:35:46.000
And then I'll even show you an iBGP right here.

00:35:46.000 --> 00:35:48.000
Just for fun.

00:35:48.000 --> 00:35:50.000
And then what we're going to do is we're going to advertise some networks over

00:35:50.000 --> 00:35:52.000
here that I have.

00:35:52.000 --> 00:35:54.000
And we're going to advertise some networks here, even though they're private

00:35:54.000 --> 00:35:55.000
networks.

00:35:55.000 --> 00:35:57.000
We're just going to use private networks for our example in this case.

00:35:57.000 --> 00:36:01.000
But I'll just show you how we can use BGP to share that information back and

00:36:01.000 --> 00:36:03.000
forth.

00:36:03.000 --> 00:36:07.000
So don't be surprised if you have to configure BGP on the exam.

00:36:07.000 --> 00:36:09.000
Don't be surprised if you have to verify BGP on the exam.

00:36:09.000 --> 00:36:13.000
So what I'm about to show you is going to be critical for your exam success.

00:36:13.000 --> 00:36:14.000
All right.

00:36:14.000 --> 00:36:18.000
So let's start off here with configuring R2 and ISPA with eBGP.

00:36:18.000 --> 00:36:20.000
So we go to R2 right now.

00:36:20.000 --> 00:36:22.000
I'm going to type in show IP protocols.

00:36:22.000 --> 00:36:25.000
And we'll see here that I'm not running BGP.

00:36:25.000 --> 00:36:26.000
We're just running that.

00:36:26.000 --> 00:36:28.000
We're just running OSPF so far.

00:36:28.000 --> 00:36:31.000
So let's type in configure terminal router.

00:36:31.000 --> 00:36:33.000
I'm going to put in BGP.

00:36:33.000 --> 00:36:35.000
And now you specify the autonomous system number.

00:36:35.000 --> 00:36:39.000
So in my case, my autonomous system number is 65,001 that we're going to be

00:36:39.000 --> 00:36:41.000
using in our example.

00:36:41.000 --> 00:36:43.000
So on the exam, whatever autonomous system they show you,

00:36:43.000 --> 00:36:46.000
that's the one you got to use.

00:36:46.000 --> 00:36:48.000
And if they don't tell you what autonomous system number it is,

00:36:48.000 --> 00:36:51.000
it's quite possible BGP might already be pre-set up.

00:36:51.000 --> 00:36:54.000
Just type in show IP protocols because if you type in do show IP protocols,

00:36:54.000 --> 00:36:57.000
I believe, let me just double check that.

00:36:57.000 --> 00:36:59.000
Yes, it shows your autonomous system number right there.

00:36:59.000 --> 00:37:00.000
All right.

00:37:00.000 --> 00:37:02.000
Or you can type in show run if it'll allow you and take a look at your

00:37:02.000 --> 00:37:03.000
running config.

00:37:03.000 --> 00:37:05.000
Show run pipe to section BGP.

00:37:05.000 --> 00:37:09.000
Do show run pipe to section BGP.

00:37:09.000 --> 00:37:10.000
All right.

00:37:10.000 --> 00:37:11.000
There you go.

00:37:11.000 --> 00:37:13.000
Now, what I want to point out to you is that when you enable BGP,

00:37:13.000 --> 00:37:16.000
you're enabling it for the whole router.

00:37:16.000 --> 00:37:17.000
The whole router.

00:37:17.000 --> 00:37:18.000
Let me be clear.

00:37:18.000 --> 00:37:22.000
The whole router.

00:37:22.000 --> 00:37:26.000
So remember like OSPF, we did it on an interface-by-interface basis?

00:37:26.000 --> 00:37:29.000
With EIGRP, we did it on an interface-by-interface basis.

00:37:29.000 --> 00:37:30.000
Okay.

00:37:30.000 --> 00:37:37.000
With BGP, it's the whole router.

00:37:37.000 --> 00:37:40.000
So you're not going to now go to interfaces and turn it on interfaces.

00:37:40.000 --> 00:37:44.000
No, that's not what you do in this case.

00:37:44.000 --> 00:37:48.000
What we're going to do is we're going to specify our neighbor now.

00:37:48.000 --> 00:37:50.000
Who is our neighbor?

00:37:50.000 --> 00:37:51.000
So in this case,

00:37:51.000 --> 00:37:56.000
our neighbor is going to be the IP address of that router that I want to

00:37:56.000 --> 00:37:58.000
form an eBGP neighborship with.

00:37:58.000 --> 00:38:01.000
So I have to know that for my ISP in this case.

00:38:01.000 --> 00:38:03.000
If my ISP doesn't tell me what their address is,

00:38:03.000 --> 00:38:05.000
I'm going to have to figure it out.

00:38:06.000 --> 00:38:09.000
Typically, you'll be able to get it from them if you contact them.

00:38:09.000 --> 00:38:15.000
203.0.113.89 in my case.

00:38:15.000 --> 00:38:18.000
Now, if you don't know and they can't tell you, you can't get a hold of them,

00:38:18.000 --> 00:38:20.000
you can always do something like this if you want.

00:38:20.000 --> 00:38:23.000
If they're allowing ICMPs, what you could do, for example,

00:38:23.000 --> 00:38:27.000
do ping 255.255.255.255.

00:38:27.000 --> 00:38:29.000
I've done this in the past and it's worked for me.

00:38:29.000 --> 00:38:34.000
But you'll see here that see the IP address 203.0.113.89?

00:38:35.000 --> 00:38:38.000
Okay, that is an IP address that is part.

00:38:38.000 --> 00:38:41.000
If I type in do show IP interface brief now,

00:38:41.000 --> 00:38:44.000
you see how that IP address is pretty close to that?

00:38:47.000 --> 00:38:50.000
So if I basically just know that my IP address on my interface is a

00:38:50.000 --> 00:38:53.000
slash 29, well, 89 is in that same subnet,

00:38:53.000 --> 00:38:55.000
so that must be the IP address.

00:38:55.000 --> 00:38:58.000
But that doesn't always necessarily work in the real world.

00:38:58.000 --> 00:39:03.000
And the reason why is because your ISP could actually be using a different

00:39:03.000 --> 00:39:05.000
IP address that they want you to peer with instead.

00:39:05.000 --> 00:39:07.000
So you've got to get that information from them.

00:39:07.000 --> 00:39:09.000
You can't just guess at it.

00:39:09.000 --> 00:39:12.000
Because they have to do a configuration on their side as well,

00:39:12.000 --> 00:39:15.000
and things are going to have to match properly.

00:39:15.000 --> 00:39:18.000
So neighbor 203.0.113.89,

00:39:18.000 --> 00:39:21.000
and then I get to type in the remote autonomous system number.

00:39:21.000 --> 00:39:24.000
Remote autonomous system number is 65,000, so whatever the ISP is.

00:39:24.000 --> 00:39:27.000
So they have to, again, you've got to get that information from them.

00:39:27.000 --> 00:39:32.000
All right, so what I've done here is I've been able to successfully

00:39:32.000 --> 00:39:37.000
define statically who I'm going to be forming a neighborship with.

00:39:37.000 --> 00:39:42.000
Now, how does the router know which interface to send the BGP message out of?

00:39:42.000 --> 00:39:44.000
It's based on this destination address.

00:39:44.000 --> 00:39:46.000
It's based on this destination address.

00:39:46.000 --> 00:39:49.000
So if I type in do show IP route,

00:39:49.000 --> 00:39:55.000
is there an interface on this device in that subnet?

00:39:55.000 --> 00:40:02.000
Or is there, I should say, an entry in the routing table

00:40:02.000 --> 00:40:12.000
that will match that IP address

00:40:12.000 --> 00:40:17.000
whereby I can use that interface to send the BGP packet out of?

00:40:17.000 --> 00:40:19.000
Yes, there is.

00:40:19.000 --> 00:40:23.000
So you have to have an entry in your routing table

00:40:23.000 --> 00:40:28.000
that will get you to this IP address in order to form a neighborship.

00:40:28.000 --> 00:40:35.000
Now, is this a valid entry that you can use to form a neighbor adjacency?

00:40:35.000 --> 00:40:40.000
The answer to that is no.

00:40:40.000 --> 00:40:45.000
You cannot use the default route to form a neighbor adjacency.

00:40:45.000 --> 00:40:51.000
It has to be something more specific than the default route.

00:40:51.000 --> 00:40:54.000
It could be a static route, an OSPF learned route, a connected route.

00:40:54.000 --> 00:40:58.000
It could be anything as long as it's not the default route

00:40:58.000 --> 00:41:06.000
to get to that particular network or to that particular address, I should say.

00:41:06.000 --> 00:41:09.000
So when you're troubleshooting BGP neighborships,

00:41:09.000 --> 00:41:11.000
you might have to pay attention to that.

00:41:11.000 --> 00:41:14.000
Why are we not forming a neighbor adjacency?

00:41:14.000 --> 00:41:21.000
Because I do not have an interface that belongs to a network

00:41:21.000 --> 00:41:25.000
that will get me to that neighbor.

00:41:25.000 --> 00:41:29.000
Like I said, the default route does not qualify for neighborships.

00:41:29.000 --> 00:41:30.000
It's just the rules.

00:41:30.000 --> 00:41:31.000
I don't make up the rules.

00:41:31.000 --> 00:41:35.000
I just teach you the rules.

00:41:35.000 --> 00:41:36.000
All right.

00:41:36.000 --> 00:41:39.000
Now, if I type in do show IP BGP summary,

00:41:39.000 --> 00:41:42.000
this is going to show you my neighborships.

00:41:42.000 --> 00:41:46.000
Now, the way I said that is kind of a little misleading.

00:41:46.000 --> 00:41:47.000
Why?

00:41:47.000 --> 00:41:48.000
Because although it shows my neighborships,

00:41:48.000 --> 00:41:52.000
what we need to realize is that this neighborship is not actually up.

00:41:52.000 --> 00:41:53.000
You see how it says up down?

00:41:53.000 --> 00:41:54.000
Never.

00:41:54.000 --> 00:41:56.000
And the state is idle.

00:41:56.000 --> 00:42:02.000
So on my neighbor, 20301389, autonomous system number 65,000,

00:42:02.000 --> 00:42:04.000
this here is a problem.

00:42:04.000 --> 00:42:06.000
Let's look at these states right now.

00:42:06.000 --> 00:42:09.000
Let's pause for a moment and go to the slides

00:42:09.000 --> 00:42:13.000
because I have a discussion later on that I might as well cover now

00:42:13.000 --> 00:42:15.000
that we're seeing idle.

00:42:15.000 --> 00:42:16.000
Okay.

00:42:16.000 --> 00:42:17.000
There's idle.

00:42:17.000 --> 00:42:19.000
What does idle actually mean?

00:42:19.000 --> 00:42:25.000
Idle means that my BGP process is currently waiting for the next attempt

00:42:25.000 --> 00:42:27.000
to establish appearing.

00:42:27.000 --> 00:42:28.000
What does that mean?

00:42:28.000 --> 00:42:29.000
It means I've already tried.

00:42:29.000 --> 00:42:31.000
I've already tried, and I have failed.

00:42:31.000 --> 00:42:32.000
What have I tried?

00:42:32.000 --> 00:42:35.000
I've tried to go from here to here.

00:42:35.000 --> 00:42:38.000
It failed, and now I'm back to here.

00:42:38.000 --> 00:42:40.000
That's what's happening right now.

00:42:40.000 --> 00:42:45.000
So idle says I'm waiting for the next attempt.

00:42:45.000 --> 00:42:47.000
Connect is what?

00:42:47.000 --> 00:42:49.000
Where your TCP connection is being established.

00:42:49.000 --> 00:42:55.000
So I tried to establish a TCP connection with that neighbor at 20301389,

00:42:55.000 --> 00:42:56.000
but it failed.

00:42:56.000 --> 00:43:00.000
The TCP connection is not successful, so I go to the active state,

00:43:00.000 --> 00:43:04.000
and then I'm going to make a second attempt while I'm in the active state,

00:43:04.000 --> 00:43:07.000
and if that does not work, then I go back to the idle state.

00:43:07.000 --> 00:43:10.000
If it does work, then I'll go on to open sent.

00:43:10.000 --> 00:43:13.000
So right now I'm kind of stuck in this loop,

00:43:13.000 --> 00:43:17.000
and I probably would never see active because it happens so fast.

00:43:17.000 --> 00:43:20.000
It's very rarely that I'm ever able to see active.

00:43:20.000 --> 00:43:23.000
I'm just refreshing right now my screen, folks, behind the scenes,

00:43:23.000 --> 00:43:26.000
and I just keep showing idle, idle, idle, idle, okay?

00:43:26.000 --> 00:43:27.000
But it happens.

00:43:27.000 --> 00:43:32.000
But if you see on the exam active or you see idle, what does that typically mean?

00:43:32.000 --> 00:43:36.000
It means you have been unable to successfully form your TCP session

00:43:36.000 --> 00:43:39.000
with a neighboring device, and the question is why?

00:43:39.000 --> 00:43:40.000
Why?

00:43:40.000 --> 00:43:42.000
Why?

00:43:42.000 --> 00:43:46.000
Because it wasn't configured yet in our case.

00:43:46.000 --> 00:43:49.000
The neighbor is not configured yet, right?

00:43:49.000 --> 00:43:51.000
It's not, okay?

00:43:51.000 --> 00:43:53.000
What else?

00:43:53.000 --> 00:43:55.000
Well, maybe we're both configured properly,

00:43:55.000 --> 00:43:59.000
but what if there's an access control list in between us that's preventing us

00:43:59.000 --> 00:44:01.000
from forming a neighbor adjacency?

00:44:01.000 --> 00:44:05.000
Well, that would be one of the reasons why we're stuck here.

00:44:05.000 --> 00:44:08.000
What if I have a route to you, I configured myself properly,

00:44:08.000 --> 00:44:11.000
you're configured properly, I have a route to you,

00:44:11.000 --> 00:44:14.000
but you're using the default route to get back to me?

00:44:14.000 --> 00:44:17.000
Well, then we would not be able to successfully form our TCP session

00:44:17.000 --> 00:44:20.000
because you would be getting my stuff, but I wouldn't probably be getting your stuff

00:44:20.000 --> 00:44:23.000
because you're not allowed to form a neighbor adjacency using the default route.

00:44:23.000 --> 00:44:25.000
So things like that come into mind, right?

00:44:26.000 --> 00:44:31.000
Anything that could prevent you from forming the TCP session,

00:44:31.000 --> 00:44:36.000
including misconfiguration of the neighbor command for BGP

00:44:36.000 --> 00:44:41.000
by specifying the wrong IP address or the wrong autonomous system number,

00:44:41.000 --> 00:44:45.000
would cause you to hang out here.

00:44:45.000 --> 00:44:47.000
So when you think about this right here,

00:44:47.000 --> 00:44:53.000
if I messed up this IP address during my configuration

00:44:53.000 --> 00:44:57.000
or I messed up this autonomous system number during my configuration,

00:44:57.000 --> 00:45:02.000
we would be stuck in idle, connect, and active, just looping through there.

00:45:02.000 --> 00:45:06.000
So if we are successful, though, then what happens,

00:45:06.000 --> 00:45:10.000
we move on to the open where we send what is called an open message.

00:45:10.000 --> 00:45:11.000
So what's an open message?

00:45:11.000 --> 00:45:16.000
An open message is used to establish the actual now BGP peering.

00:45:16.000 --> 00:45:20.000
So you have your TCP session set up once you get beyond active,

00:45:20.000 --> 00:45:23.000
and now we've got to exchange the actual BGP parameters now

00:45:23.000 --> 00:45:25.000
and everything else that goes along with it.

00:45:25.000 --> 00:45:30.000
And so open used to establish the peering by exchanging the parameters,

00:45:30.000 --> 00:45:33.000
things like your autonomous system number, authentication values,

00:45:33.000 --> 00:45:36.000
and anything else that you have as part of your BGP config.

00:45:36.000 --> 00:45:38.000
And if all of that is successful,

00:45:38.000 --> 00:45:41.000
eventually we get to what is called the established state.

00:45:41.000 --> 00:45:45.000
And so established means that we have a successful peering in place,

00:45:45.000 --> 00:45:48.000
and now we can actually start exchanging update messages,

00:45:48.000 --> 00:45:51.000
meaning we can, I'll use the word, synchronize with each other,

00:45:51.000 --> 00:45:54.000
but you're not really synchronizing like you are with OSPF, okay?

00:45:54.000 --> 00:45:58.000
But I can send you BGP information and you can send me BGP information.

00:45:58.000 --> 00:46:01.000
So that's what the update message is, used to exchange the path attributes,

00:46:01.000 --> 00:46:05.000
the prefixes, when adding and withdrawing routes from the table.

00:46:05.000 --> 00:46:10.000
So once we establish our session fully, establish is the right word for BGP,

00:46:10.000 --> 00:46:13.000
then we can send update messages to teach each other,

00:46:13.000 --> 00:46:16.000
and then anytime anything changes down the road,

00:46:16.000 --> 00:46:19.000
we just continue to send update messages to each other to update each other

00:46:19.000 --> 00:46:21.000
of those changes when it comes to the networks and prefixes

00:46:21.000 --> 00:46:24.000
and attributes and everything else.

00:46:24.000 --> 00:46:27.000
Keep-alives are going to be sent periodically to maintain our peering as well,

00:46:27.000 --> 00:46:33.000
and the reason why is because the TCP session will break down and fall apart

00:46:33.000 --> 00:46:38.000
if we don't keep updating ourselves if the TCP session is alive as well.

00:46:38.000 --> 00:46:44.000
Because how does a TCP session stay active when you are communicating

00:46:44.000 --> 00:46:46.000
between a client and a server?

00:46:46.000 --> 00:46:47.000
Let me repeat that.

00:46:47.000 --> 00:46:51.000
How does a TCP session remain active, or not active, I can't use the word active,

00:46:51.000 --> 00:46:56.000
how does a TCP session remain established when a client is talking to a web server?

00:46:56.000 --> 00:46:57.000
Well, just keep talking.

00:46:57.000 --> 00:46:59.000
That's right, just keep talking.

00:46:59.000 --> 00:47:02.000
As long as you keep talking, as long as you keep doing things,

00:47:02.000 --> 00:47:05.000
the TCP session will stay established.

00:47:05.000 --> 00:47:09.000
As soon as you stop talking, it's like within approximately nine seconds,

00:47:09.000 --> 00:47:12.000
your TCP session would be torn down.

00:47:13.000 --> 00:47:16.000
So with BGP, we need a way to keep that session up and running.

00:47:16.000 --> 00:47:18.000
We need a way to keep it active, not active.

00:47:18.000 --> 00:47:19.000
Ah, established.

00:47:19.000 --> 00:47:22.000
Like you said, that active word can be misleading.

00:47:22.000 --> 00:47:23.000
I know.

00:47:23.000 --> 00:47:24.000
You see, there you go.

00:47:24.000 --> 00:47:29.000
You got me saying it now when I'm not supposed to be saying.

00:47:29.000 --> 00:47:33.000
So how do we keep that TCP session established with BGP?

00:47:33.000 --> 00:47:35.000
We are going to have a keep-alive.

00:47:35.000 --> 00:47:38.000
That goes back and forth to make sure it stays up for us.

00:47:38.000 --> 00:47:42.000
And then a notification with BGP is going to be generated

00:47:42.000 --> 00:47:44.000
and sent any time an issue arises.

00:47:44.000 --> 00:47:48.000
If there's an error that needs a BGP appearing to be reset

00:47:48.000 --> 00:47:52.000
or anything like that, notifications can be used to accomplish that.

00:47:52.000 --> 00:47:56.000
So these, I would know these, like you see them listed here, folks,

00:47:56.000 --> 00:48:00.000
like the definitions of them, as well as the definitions of these

00:48:00.000 --> 00:48:01.000
and what I described to them.

00:48:01.000 --> 00:48:03.000
Because you never know when you might be asked,

00:48:03.000 --> 00:48:04.000
hey, why are you in the idle state right now?

00:48:04.000 --> 00:48:07.000
Oh, because we haven't been able to successfully establish our TCP peering.

00:48:07.000 --> 00:48:08.000
Stuff like that.

00:48:08.000 --> 00:48:10.000
Or they might get very specific and say,

00:48:10.000 --> 00:48:13.000
because you're waiting for the next attempt to establish a peering.

00:48:13.000 --> 00:48:16.000
So I'd keep that in mind for the certification exam,

00:48:16.000 --> 00:48:18.000
just to make sure that you have all the information

00:48:18.000 --> 00:48:22.000
and details that you need to be successful.

00:48:22.000 --> 00:48:23.000
All right.

00:48:23.000 --> 00:48:25.000
So with that in mind, let's get back to our diagram.

00:48:25.000 --> 00:48:30.000
Let's get back to our configuration of BGP.

00:48:30.000 --> 00:48:31.000
All right.

00:48:31.000 --> 00:48:36.000
So we've configured one side so far successfully.

00:48:36.000 --> 00:48:38.000
Let's go ahead to ISPA.

00:48:38.000 --> 00:48:41.000
Now, the ISP would do this themselves, not me.

00:48:41.000 --> 00:48:45.000
I wouldn't be the one responsible for doing this.

00:48:45.000 --> 00:48:54.000
But we'll type in router BGP, their autonomous system number is 65,000.

00:48:54.000 --> 00:48:56.000
And then neighbor, who's their neighbor?

00:48:56.000 --> 00:48:58.000
I am their neighbor, so they would have my IP address,

00:48:58.000 --> 00:49:04.000
203.0.113.91 is the IP address of R2.

00:49:04.000 --> 00:49:07.000
And then what is the remote autonomous system number?

00:49:07.000 --> 00:49:11.000
The remote autonomous system number is 65001.

00:49:11.000 --> 00:49:13.000
So we see here relatively quickly the neighborship goes up.

00:49:13.000 --> 00:49:15.000
It doesn't necessarily happen that quick.

00:49:15.000 --> 00:49:17.000
It can take a little time to come up.

00:49:17.000 --> 00:49:19.000
BGP is a very slow protocol.

00:49:19.000 --> 00:49:21.000
But now we are successfully up.

00:49:21.000 --> 00:49:25.000
So if we come back to this output, let's take a peek at that now,

00:49:25.000 --> 00:49:29.000
you'll see that it actually has a number instead.

00:49:29.000 --> 00:49:36.000
So anytime you see a word here, that means something is wrong.

00:49:36.000 --> 00:49:42.000
Anytime you see a number here, that means something is right.

00:49:42.000 --> 00:49:44.000
So what does the number zero mean?

00:49:44.000 --> 00:49:48.000
The number zero means we just haven't shared any routes with each other.

00:49:48.000 --> 00:49:55.000
We're neighbors for 40 seconds now, but we haven't exchanged any routes

00:49:55.000 --> 00:49:58.000
because there's nothing to share with each other yet.

00:49:58.000 --> 00:50:01.000
So, again, you don't just dynamically share stuff.

00:50:01.000 --> 00:50:06.000
You have to identify what you're going to share, and then that can be shared.

00:50:06.000 --> 00:50:10.000
Now, if you learn something, you'll automatically share it.

00:50:10.000 --> 00:50:13.000
But with EIGP and OSPF, remember,

00:50:13.000 --> 00:50:15.000
if your interface was enabled for the routing process,

00:50:15.000 --> 00:50:18.000
the network ID was injected, then you share it.

00:50:18.000 --> 00:50:20.000
Okay, well, that doesn't happen with BGP.

00:50:20.000 --> 00:50:22.000
If you want to share something locally,

00:50:22.000 --> 00:50:25.000
you're going to have to manually input what you want to share locally,

00:50:25.000 --> 00:50:32.000
and you'll dynamically share anything you learn from other routers as well.

00:50:32.000 --> 00:50:34.000
Where does the word established come up?

00:50:34.000 --> 00:50:41.000
So if I type in show IPBGP neighbor, and we put in the neighbor address,

00:50:41.000 --> 00:50:46.000
you'll see here that the established keyword is right there.

00:50:46.000 --> 00:50:50.000
So we have a fully established neighbor adjacency with each other.

00:50:50.000 --> 00:50:52.000
Let's scroll down quite a bit here

00:50:52.000 --> 00:50:55.000
because I want to show you the server-client relationship.

00:50:55.000 --> 00:51:00.000
So you'll see here that I am the client.

00:51:00.000 --> 00:51:03.000
The ISP is the server.

00:51:03.000 --> 00:51:04.000
How do I know that?

00:51:04.000 --> 00:51:07.000
Because they're using TCP port 179.

00:51:07.000 --> 00:51:12.000
They're the server, and I'm using an ephemeral port number 62444.

00:51:12.000 --> 00:51:15.000
Therefore, I am the client.

00:51:15.000 --> 00:51:17.000
Also, you see the time to live here?

00:51:17.000 --> 00:51:24.000
That time to live is the default for EBGP.

00:51:24.000 --> 00:51:30.000
EBGP's time to live is 1.

00:51:30.000 --> 00:51:32.000
What does that mean?

00:51:32.000 --> 00:51:33.000
Well, it's what I talked about earlier.

00:51:33.000 --> 00:51:36.000
You have to be directly connected to each other.

00:51:36.000 --> 00:51:39.000
You have to be within one hop away from each other.

00:51:39.000 --> 00:51:41.000
So when I send the message out to this interface,

00:51:41.000 --> 00:51:47.000
the next router that gets it must be the router I'm trying to form a peering with

00:51:47.000 --> 00:51:50.000
because of that number right there.

00:51:50.000 --> 00:51:52.000
So that number can be changed.

00:51:52.000 --> 00:51:59.000
Like I said, let me just show you that here, BGP.

00:51:59.000 --> 00:52:03.000
I am drawing a blank massively on the command now.

00:52:03.000 --> 00:52:06.000
Oh, my gosh.

00:52:06.000 --> 00:52:13.000
Not maximum pass.

00:52:13.000 --> 00:52:17.000
Man, I was thinking about it like two seconds ago.

00:52:18.000 --> 00:52:37.000
EBGP.

00:52:37.000 --> 00:52:38.000
No, no, no, no.

00:52:38.000 --> 00:52:39.000
What is it?

00:52:39.000 --> 00:52:44.000
Yeah, yeah.

00:52:44.000 --> 00:52:45.000
Yeah, I just remembered.

00:52:45.000 --> 00:52:47.000
It's a part of the neighbor command.

00:52:47.000 --> 00:52:49.000
That's why I'm drawing a blank right now.

00:52:49.000 --> 00:52:52.000
And it's going to be somebody just chatted in.

00:52:52.000 --> 00:52:53.000
Yeah, BGP.

00:52:53.000 --> 00:52:54.000
There it is.

00:52:54.000 --> 00:52:55.000
There it is.

00:52:55.000 --> 00:52:56.000
Multi-hop.

00:52:56.000 --> 00:52:57.000
There is the command right there.

00:52:57.000 --> 00:52:58.000
That's what I was looking for.

00:52:58.000 --> 00:53:09.000
So that right there is unrecognized command.

00:53:10.000 --> 00:53:14.000
How can that be an unrecognized command?

00:53:14.000 --> 00:53:32.000
Neighbor 203-01-13.

00:53:32.000 --> 00:53:33.000
There it is.

00:53:33.000 --> 00:53:35.000
Yeah.

00:53:35.000 --> 00:53:38.000
Yay.

00:53:38.000 --> 00:53:41.000
It didn't copy the E for me, even though it was highlighted.

00:53:41.000 --> 00:53:42.000
Strange.

00:53:42.000 --> 00:53:43.000
All right.

00:53:43.000 --> 00:53:45.000
So now your maximum hop.

00:53:45.000 --> 00:53:47.000
Let me just set it to five as an example.

00:53:47.000 --> 00:53:48.000
All right.

00:53:48.000 --> 00:53:50.000
Let me just set it to five just so you can see the output now.

00:53:50.000 --> 00:53:55.000
There we go.

00:53:55.000 --> 00:53:56.000
Scroll down.

00:53:56.000 --> 00:54:01.000
You'll see that now it's set to five, which means that could be five router hops away

00:54:01.000 --> 00:54:05.000
and form a neighbor adjacency using EBGP.

00:54:05.000 --> 00:54:13.000
So you only need to use that command if you are not directly connected to each other.

00:54:13.000 --> 00:54:18.000
So on the exam, if all of a sudden the diagram shows a router here and then there's multiple

00:54:18.000 --> 00:54:22.000
routers in between and the neighborhood's not forming, well, if the time to live is

00:54:22.000 --> 00:54:24.000
the default of one, that's the reason why it's not working.

00:54:24.000 --> 00:54:28.000
You're going to have to use the EBGP multi-hop command in order to accomplish that.

00:54:28.000 --> 00:54:29.000
All right.

00:54:29.000 --> 00:54:30.000
There we go.

00:54:35.000 --> 00:54:56.000
So let's go ahead and remove this for a second because I want to reconfigure it.

00:54:56.000 --> 00:55:01.000
But what I want to do is I want to put in the wrong autonomous system number and see

00:55:01.000 --> 00:55:03.000
what happens.

00:55:03.000 --> 00:55:10.000
So for example, the service provider, I accidentally typed in a one.

00:55:10.000 --> 00:55:19.000
Well, who's autonomous system number is that?

00:55:19.000 --> 00:55:24.000
That's my autonomous system number, right?

00:55:24.000 --> 00:55:27.000
That's my autonomous system number.

00:55:27.000 --> 00:55:30.000
So notice all the error messages I'm getting.

00:55:30.000 --> 00:55:32.000
Why is that?

00:55:32.000 --> 00:55:41.000
Because that neighbor, that IP address that I specified in the config, 20301389, okay,

00:55:41.000 --> 00:55:45.000
well, they are not in autonomous system 65,001.

00:55:45.000 --> 00:55:46.000
They are in what?

00:55:46.000 --> 00:55:49.000
Autonomous system 65,000.

00:55:49.000 --> 00:55:55.000
So you have to make sure that you get that number perfect and correct.

00:55:55.000 --> 00:56:01.000
So let me erase that command and let me put in, for example, let's put in one that's not

00:56:01.000 --> 00:56:02.000
mine.

00:56:02.000 --> 00:56:04.000
So in this case, I'm not even going to put my own in.

00:56:04.000 --> 00:56:05.000
Oops, that's a wait.

00:56:05.000 --> 00:56:08.000
Oh, no, that will still work.

00:56:08.000 --> 00:56:12.000
But you'll see even then, right, wrong autonomous system number.

00:56:12.000 --> 00:56:17.000
So although in the real world, if you got syslog messaging turned on, you're going to

00:56:17.000 --> 00:56:18.000
get notified.

00:56:18.000 --> 00:56:22.000
Be mindful in the exam, you're never going to get notifications about what's going on.

00:56:22.000 --> 00:56:26.000
They're never going to show you syslog messages if you're trying to troubleshoot a BGP issue.

00:56:27.000 --> 00:56:32.000
It's about recognizing or looking at the config and realizing, hey, this is misconfigured

00:56:32.000 --> 00:56:34.000
in the config.

00:56:34.000 --> 00:56:39.000
The autonomous system number should be 65,000, not 65,000 whatever is listed here right now.

00:56:47.000 --> 00:56:49.000
And the same thing will be true with the IP address as well.

00:56:49.000 --> 00:56:54.000
If I specify an IP address and it's the wrong IP address, then what's going to happen is

00:56:54.000 --> 00:56:57.000
as I'm reaching out to that IP address, nobody's going to be there to respond to me.

00:56:57.000 --> 00:57:00.000
If nobody's there to respond to me, then I can't form a neighbor adjacency.

00:57:00.000 --> 00:57:02.000
So that's what I was saying.

00:57:02.000 --> 00:57:07.000
If you're looking at your output for your neighborship, show IP BGP summary, and you

00:57:07.000 --> 00:57:11.000
see you're in idle or active state or anything like that, double check that IP.

00:57:11.000 --> 00:57:13.000
Double check that autonomous system number.

00:57:13.000 --> 00:57:17.000
Double check to see if anything's even configured as it needs to be.

00:57:17.000 --> 00:57:21.000
So that way there in the end, you can compare and contrast what needs to be there versus

00:57:21.000 --> 00:57:24.000
what you have and then solve the questions that way.

00:57:30.000 --> 00:57:31.000
Yeah.

00:57:31.000 --> 00:57:33.000
So question coming in about loopback addresses.

00:57:33.000 --> 00:57:39.000
If, for example, you were using a loopback address here and you were using a loopback

00:57:39.000 --> 00:57:45.000
address here, how many hops are those loopback addresses away from each other?

00:57:45.000 --> 00:57:49.000
So what if I was trying to form a neighborship from the loopback to the loopback?

00:57:49.000 --> 00:57:52.000
How many hops are they away from each other?

00:57:52.000 --> 00:57:53.000
Okay.

00:57:53.000 --> 00:57:58.000
Well, when it leaves this router, that's one hop to here.

00:57:58.000 --> 00:58:03.000
And what most people don't realize is that to go to the loopback, that's another hop.

00:58:03.000 --> 00:58:08.000
So hop one, hop two, that's actually two hops when it's all said and done.

00:58:08.000 --> 00:58:14.000
So if you ever see a scenario where it's loopback to loopback, that's actually two hops away,

00:58:14.000 --> 00:58:15.000
not one hop.

00:58:16.000 --> 00:58:20.000
So you will definitely need to change what?

00:58:20.000 --> 00:58:22.000
The eBGP multi-hop parameter in that case.

00:58:35.000 --> 00:58:38.000
Let's configure authentication between these two routers now.

00:58:39.000 --> 00:58:41.000
So eBGP authentication is pretty simple.

00:58:42.000 --> 00:58:44.000
Again, you're going to use the neighbor command.

00:58:47.000 --> 00:58:51.000
And then you're going to specify the IP address of the neighbor you want to do authentication with.

00:58:53.000 --> 00:58:57.000
And then the keyword that you're looking for is the good old password keyword.

00:58:58.000 --> 00:59:02.000
And then the keyword that you're looking for is the good old password keyword.

00:59:09.000 --> 00:59:12.000
Specify your password that you want to use.

00:59:12.000 --> 00:59:16.000
So we use Cisco Rocks.

00:59:17.000 --> 00:59:23.000
So now if we go to the ISP, we'll have to do the same thing except specify the other address, the information.

00:59:24.000 --> 00:59:30.000
So in this case, neighbor 203011391, password Cisco Rocks.

00:59:33.000 --> 00:59:39.000
Now before I hit enter there, let's go back to R2 and let's do do clear IP BGP star.

00:59:40.000 --> 00:59:42.000
Let's just hard reset the BGP neighborship.

00:59:44.000 --> 00:59:50.000
And when it comes back up, we're going to see, we should see here password mismatch information

00:59:50.000 --> 00:59:53.000
because we haven't officially configured it on the other side yet.

00:59:53.000 --> 00:59:57.000
So as you can see, we're using MD5 for authentication with BGP.

00:59:58.000 --> 01:00:04.000
So even though I'm putting in a password in plain text, we're using MD5 when it's all said and done by default.

01:00:10.000 --> 01:00:12.000
So let's go over and configure ISPA.

01:00:12.000 --> 01:00:18.000
And then we should see that our neighborship will form and everything will be good and these routers will be happy.

01:00:24.000 --> 01:00:28.000
So as you can see, authentication is very, very simple with BGP.

01:00:32.000 --> 01:00:36.000
Let me throw that other neighbor command in there, the EBGP1.

01:00:37.000 --> 01:00:44.000
Just so you have it as a reference for later on in case you come back and review this and you want to make some notes about this stuff.

01:00:46.000 --> 01:00:51.000
Notice that when you're configuring BGP, the list just keeps getting bigger and bigger and bigger when it comes to your commands.

01:00:52.000 --> 01:00:54.000
So here's another thing I have to talk about with you.

01:00:54.000 --> 01:00:59.000
The way I'm configuring BGP right now is the old classic BGP.

01:01:00.000 --> 01:01:04.000
But you have to remember that BGP is a multi-protocol solution.

01:01:05.000 --> 01:01:09.000
And so what it has the ability to do is use what are called address families.

01:01:10.000 --> 01:01:14.000
So we are actually today using what is called multi-protocol BGP version number four.

01:01:15.000 --> 01:01:19.000
Multi-protocol BGP version number four is a multi-protocol BGP version number four.

01:01:20.000 --> 01:01:23.000
And it's a multi-protocol BGP version number four.

01:01:23.000 --> 01:01:25.000
Multi-protocol BGP version number four.

01:01:26.000 --> 01:01:28.000
Multi-protocol BGP version number four.

01:01:29.000 --> 01:01:33.000
So you might see it listed as MP-BGP on the certification exam.

01:01:36.000 --> 01:01:41.000
And what that means is that if we look here, you'll see that you have what is called address family.

01:01:42.000 --> 01:01:44.000
So if I just click on address families right now,

01:01:47.000 --> 01:01:55.000
you'll see that I can do IPv4 address families, IPv6 address families, Layer 2 VPN address families,

01:01:55.000 --> 01:01:56.000
NSAP address families.

01:01:56.000 --> 01:01:57.000
I'm not going to get into the difference between all of these.

01:01:57.000 --> 01:02:00.000
But I mean, you could kind of figure out what IPv4 and IPv6 are.

01:02:01.000 --> 01:02:02.000
That's not too hard.

01:02:02.000 --> 01:02:09.000
But look, if I go under IPv4 now, you'll see that I can do even more different types, I should say,

01:02:09.000 --> 01:02:11.000
of address families for IPv4.

01:02:11.000 --> 01:02:17.000
We could do a unicast address family, a multicast address family, a VRF address family

01:02:18.000 --> 01:02:21.000
for VPN routing and forwarding and stuff like that.

01:02:21.000 --> 01:02:29.000
So definitely a lot of different abilities or a lot of different types of situations and scenarios we could use BGP in.

01:02:30.000 --> 01:02:37.000
So when you are doing a classic BGP config, I mean, you could do this.

01:02:37.000 --> 01:02:43.000
But as soon as you start needing configs for IPv4 and IPv6 and everything else, this doesn't really work for you anymore.

01:02:43.000 --> 01:02:49.000
And so what you would do for IPv4 is you'd configure address family IPv4 unicast.

01:02:49.000 --> 01:02:50.000
That's the same thing.

01:02:51.000 --> 01:02:59.000
So address family IPv4 unicast is the same as what we're doing here underneath the global config.

01:02:59.000 --> 01:03:04.000
Let's see if by doing that, it changed anything for us in our output.

01:03:04.000 --> 01:03:05.000
See what happened now?

01:03:05.000 --> 01:03:09.000
Under address family IPv4, it's done what is called a neighbor activation now.

01:03:10.000 --> 01:03:12.000
What is the neighbor activation?

01:03:12.000 --> 01:03:21.000
The neighbor activation means that that particular neighbor, 203.0.1.1.3.89 is now activated for IPv4.

01:03:21.000 --> 01:03:23.000
Now, why is this activation there?

01:03:23.000 --> 01:03:28.000
The activation is there because when it comes to all the other address families,

01:03:29.000 --> 01:03:34.000
you have to activate the neighbors before they actually get usable.

01:03:34.000 --> 01:03:37.000
With IPv4, they automatically get activated.

01:03:38.000 --> 01:03:40.000
But with IPv6, they wouldn't.

01:03:40.000 --> 01:03:43.000
You would actually have to type in neighbor, the address, and activate as well.

01:03:44.000 --> 01:03:47.000
So typically what's going to happen is you're going to specify your neighbor commands up here first,

01:03:47.000 --> 01:03:50.000
like neighbor remote autonomous system, neighbor this, neighbor that.

01:03:51.000 --> 01:03:54.000
But then when you get down to specific IPv4-related things,

01:03:54.000 --> 01:03:57.000
you'd have to activate the neighbor and do the specific IPv4-related things.

01:03:57.000 --> 01:04:02.000
Under IPv6, activate the neighbor, specific IPv6 neighbor thing.

01:04:02.000 --> 01:04:04.000
So I'm in the address family right now.

01:04:04.000 --> 01:04:09.000
If you take a look here, you can do things like auto-summarization, aggregate addresses, which is a summary.

01:04:09.000 --> 01:04:13.000
You can do default metrics, distribute lists, maximum pass, network.

01:04:13.000 --> 01:04:15.000
And there's even neighbor commands in here as well.

01:04:15.000 --> 01:04:18.000
So if I go into the neighbor command, you can specify the neighbor.

01:04:18.000 --> 01:04:24.000
But you'll see that the options are going to be slightly different than what you have under the global config.

01:04:24.000 --> 01:04:30.000
So if you've got the active, but then you've got a lot of different things like allow policy, allow ASN, AS override.

01:04:30.000 --> 01:04:32.000
We'll talk about some of those a little later on.

01:04:32.000 --> 01:04:33.000
Next hop self.

01:04:33.000 --> 01:04:39.000
So these are very specific things, very specific little features, functions that you can manipulate and modify with BGP.

01:04:39.000 --> 01:04:45.000
But I'm just trying to show you that the address family may or may not show up on this certification exam.

01:04:46.000 --> 01:04:52.000
But definitely going down the road, you need to become familiar with just the construct of how you configure BGP.

01:04:53.000 --> 01:05:01.000
So if you do see address family on the exam, just realize that what you see here, combined with whatever you would see in here,

01:05:01.000 --> 01:05:06.000
is the stuff you want to pay attention to for the IPV4 examples of BGP on the certification exam.

01:05:06.000 --> 01:05:11.000
If they don't have the address family specified, then you only have to worry about what's in the top config right there.

01:05:15.000 --> 01:05:18.000
The joys of having multiple ways of configuring the same things, right?

01:05:19.000 --> 01:05:20.000
All right.

01:05:20.000 --> 01:05:26.000
So now I want to take a peek at how we can shut down a neighbor if we ever need to.

01:05:27.000 --> 01:05:29.000
What did I mean by shut down a neighbor?

01:05:29.000 --> 01:05:40.000
Well, just think about the fact that if you all of a sudden need to stop that one specific neighbor, but no other neighbor, right?

01:05:40.000 --> 01:05:41.000
Why might that be?

01:05:41.000 --> 01:05:43.000
Well, I mean, could be for any reasons.

01:05:43.000 --> 01:05:50.000
The fact of the matter is you don't want to delete your entire BGP config, because that would affect every other neighbor as well.

01:05:51.000 --> 01:05:54.000
So you have the ability to enable and disable your neighbors.

01:06:00.000 --> 01:06:06.000
So if I type in something like neighbor, and then put in the IP address of that neighbor,

01:06:07.000 --> 01:06:09.000
and then put in the IP address of that neighbor,

01:06:15.000 --> 01:06:21.000
all right, you'll see here that I am looking for what is called the shutdown option, but it's not here.

01:06:22.000 --> 01:06:26.000
And that's one of the things you're going to find with BGP as you play around with it more and more and more,

01:06:26.000 --> 01:06:32.000
is that some of the commands, now that you have address family enabled, well, some of them are going to be here,

01:06:32.000 --> 01:06:34.000
some of them are going to be in the global mode.

01:06:34.000 --> 01:06:36.000
So shutdown is one of those global commands.

01:06:36.000 --> 01:06:40.000
So let me back out, and it's going to be neighbor so-and-so.

01:06:40.000 --> 01:06:43.000
And if we scroll down to the bottom, we should see shutdown in here somewhere.

01:06:44.000 --> 01:06:45.000
There it is.

01:06:45.000 --> 01:06:48.000
So if I type in shutdown, that'll just shut down this neighborhood,

01:06:48.000 --> 01:06:51.000
but it doesn't shut down any other neighborhood that I would actually have.

01:06:52.000 --> 01:06:56.000
So, for example, if you had five or six neighbors, and you want to disable one of those neighbors,

01:06:56.000 --> 01:07:00.000
but you don't want to delete the config of that neighbor, you don't want to delete the config of any other neighbor,

01:07:00.000 --> 01:07:01.000
then what are you going to do?

01:07:01.000 --> 01:07:05.000
You're going to go ahead, and you are going to administratively shut down that neighbor with the command.

01:07:05.000 --> 01:07:11.000
And if you look at the output of do show IP BGP summary now, you'll see it actually says admin in brackets.

01:07:11.000 --> 01:07:18.000
So if you ever see admin in brackets, idle admin in brackets, that means somebody typed this command in right here.

01:07:32.000 --> 01:07:37.000
If you ever want to set your BGP router ID, you can type in BGP router ID.

01:07:37.000 --> 01:07:47.000
So just like a router ID in EIGRP, a router ID in OSPF is a 32-bit number that you utilize to uniquely identify the device

01:07:47.000 --> 01:07:52.000
amongst the other peering devices in that environment.

01:07:53.000 --> 01:07:58.000
So by default, your router ID is going to be chosen the same way as it was with OSPF.

01:07:58.000 --> 01:08:04.000
If it's not manually configured, or it's not specified based on the other options here,

01:08:04.000 --> 01:08:10.000
like you can specify the actual interface IP address if you want to use this interface for the router ID if you wanted to,

01:08:10.000 --> 01:08:11.000
or manually configure it.

01:08:11.000 --> 01:08:15.000
If you haven't used OSPF, you can specify the actual IP address for the router ID.

01:08:15.000 --> 01:08:17.000
Then it's going to look for loopback interfaces.

01:08:17.000 --> 01:08:19.000
Use the highest IP address amongst the loopback interfaces.

01:08:19.000 --> 01:08:23.000
If there's no loopback interfaces, it's going to use the highest IP address amongst the remaining interfaces.

01:08:29.000 --> 01:08:35.000
So with that said, let me just quickly show you how to do an IBGP neighborship between two routers.

01:08:35.000 --> 01:08:37.000
Notice how they're not directly connected to each other.

01:08:37.000 --> 01:08:39.000
Obviously, they're not directly connected to each other.

01:08:39.000 --> 01:08:43.000
Let me just quickly show you how to do an IBGP neighborship between two routers.

01:08:43.000 --> 01:08:46.000
Notice how they're not directly connected to each other, R1 and R2.

01:08:51.000 --> 01:09:03.000
Now, the thing about BGP in this type of scenario is that we have multiple ways that we can form our TCP session.

01:09:03.000 --> 01:09:05.000
You see that?

01:09:05.000 --> 01:09:10.000
So what's going to decide the way we go to form our TCP session?

01:09:10.000 --> 01:09:12.000
That's going to be our routing table.

01:09:14.000 --> 01:09:19.000
The problem we run into in this case is that when the BGP message is sent out that interface,

01:09:19.000 --> 01:09:26.000
that is going to be the source of the BGP message, the source of the BGP message.

01:09:26.000 --> 01:09:28.000
Therefore, it's coming from that IP address.

01:09:28.000 --> 01:09:38.000
So when this router gets it, it's that source IP address that this router uses to determine if it should form a neighborship with it or not.

01:09:38.000 --> 01:09:44.000
So when you type in the neighbor command on this router down here, when you type in neighbor and you put in an IP address,

01:09:46.000 --> 01:09:53.000
this IP address has to match the interface that was used to send the packet.

01:09:55.000 --> 01:09:56.000
So what does that mean?

01:09:56.000 --> 01:10:02.000
Does that mean I would need a neighborship for every single interface IP address that could be used to send the packet?

01:10:02.000 --> 01:10:04.000
Kind of, doesn't it?

01:10:04.000 --> 01:10:05.000
Well, that's no good.

01:10:05.000 --> 01:10:06.000
That's no good.

01:10:07.000 --> 01:10:13.000
So whenever you're doing IBGP peerings, because there will typically be multiple paths that you can utilize,

01:10:13.000 --> 01:10:16.000
it's better to peer with the loopback interfaces.

01:10:17.000 --> 01:10:21.000
So you would definitely want to create loopback interfaces on your device for this purpose.

01:10:22.000 --> 01:10:30.000
So loopback 192, and we'll give it an IP address of 168.255.2 in this example, slash 32.

01:10:30.000 --> 01:10:35.000
And I'll create one 192.168.255.1, slash 32.

01:10:35.000 --> 01:10:38.000
And then I'm going to inject those into OSPF.

01:10:38.000 --> 01:10:41.000
Remember, so that way there, R1 and R2 can reach each other.

01:10:41.000 --> 01:10:43.000
So remember, we're using OSPF.

01:10:43.000 --> 01:10:45.000
So I might as well inject those into OSPF.

01:10:45.000 --> 01:10:46.000
So let's just create those quickly.

01:10:46.000 --> 01:11:00.000
So I go over to R1, and I'm going to type in interface loopback 192, IP address 192.168.255.1, 255.255.255.255,

01:11:00.000 --> 01:11:05.000
IP OSPF OSPF1 area 0.

01:11:05.000 --> 01:11:08.000
And then let's go to R2 and do the exact same thing.

01:11:08.000 --> 01:11:21.000
So interface loopback 192, IP address 192.168.255.2, 255.255.255.255.

01:11:21.000 --> 01:11:25.000
I think we already have this interface configured from when we were doing our,

01:11:25.000 --> 01:11:29.000
I think I did the router ID example OSPF, because that's why I don't see it coming up right now.

01:11:29.000 --> 01:11:31.000
I think it's because we already had it.

01:11:31.000 --> 01:11:35.000
And then we have now IP OSPF1 area 0.

01:11:38.000 --> 01:11:43.000
Okay.

01:11:43.000 --> 01:11:51.000
So now if I type in do show IP route, we should see those routes in the routing table.

01:11:51.000 --> 01:11:56.000
So, all right, so there's 192.168.255.1.

01:11:56.000 --> 01:11:58.000
All right, so here's the plan now.

01:11:58.000 --> 01:12:01.000
There are multiple ways that I can still get to you.

01:12:01.000 --> 01:12:04.000
As you can see, I can get this way or this way in order to get there.

01:12:04.000 --> 01:12:08.000
So what we're going to do is we're going to be very specific with our BGP configuration here.

01:12:08.000 --> 01:12:17.000
When we actually specify our neighborships, we are going to specify the fact that we want to peer

01:12:17.000 --> 01:12:22.000
using our loopback interface instead of the exiting interface's IP address.

01:12:22.000 --> 01:12:23.000
So watch this.

01:12:23.000 --> 01:12:28.000
I'm going to go back to router BGP configuration mode for 65,001.

01:12:28.000 --> 01:12:33.000
I'm going to say my neighbor is at 192.168.255.1.

01:12:33.000 --> 01:12:35.000
So I'm going to use its loopback address.

01:12:35.000 --> 01:12:37.000
And there in remote autonomous system what?

01:12:37.000 --> 01:12:39.000
Well, if you're IBGP, that's what you do.

01:12:39.000 --> 01:12:42.000
So IBGP means you put the same autonomous system number.

01:12:42.000 --> 01:12:45.000
That's how the router automatically knows it's IBGP.

01:12:45.000 --> 01:12:49.000
So if the autonomous system number here is different than there, that means EBGP.

01:12:49.000 --> 01:12:52.000
If it's the same, that means IBGP.

01:12:52.000 --> 01:12:53.000
All right, so I've done that.

01:12:53.000 --> 01:12:58.000
Now what I'm going to do is I'm going to go to address family configuration mode for IPv4 Unicast,

01:12:58.000 --> 01:13:01.000
and I'm going to type in neighbor.

01:13:01.000 --> 01:13:04.000
I'm going to put in this address here.

01:13:04.000 --> 01:13:12.000
And I'm going to say update source.

01:13:12.000 --> 01:13:13.000
And let me guess.

01:13:13.000 --> 01:13:16.000
That is under, yep, I did it again.

01:13:16.000 --> 01:13:18.000
It's under the other configuration.

01:13:18.000 --> 01:13:19.000
I do that every time.

01:13:19.000 --> 01:13:24.000
Even when I taught it in an RC, I made the same mistake all these years,

01:13:24.000 --> 01:13:27.000
and I still may update source loopback 192.

01:13:27.000 --> 01:13:29.000
All right, so now what does that mean?

01:13:29.000 --> 01:13:32.000
Well, if you type in do, show, run, pipe to section router BGP,

01:13:32.000 --> 01:13:38.000
what you're seeing is that I am now telling my router, hey,

01:13:38.000 --> 01:13:44.000
any time that you want to communicate with this router,

01:13:44.000 --> 01:13:47.000
whether it's to form a neighborhood or send an update,

01:13:47.000 --> 01:13:51.000
use the IP address of your loopback interface.

01:13:51.000 --> 01:13:56.000
So now all my packets, BGP packets that go to 192.168.255.1

01:13:56.000 --> 01:14:01.000
are going to be sourced from 192.168.255.2.

01:14:01.000 --> 01:14:02.000
So what does that mean?

01:14:02.000 --> 01:14:07.000
It means now when I go over to R1, when I specify neighbor as 192.168.255.2, right,

01:14:07.000 --> 01:14:10.000
it matches this IP address here.

01:14:10.000 --> 01:14:11.000
That's what I'm trying to do.

01:14:11.000 --> 01:14:13.000
I'm trying to make sure that I'm matching the sending

01:14:13.000 --> 01:14:16.000
and receiving IP addresses for the neighborhoods

01:14:16.000 --> 01:14:18.000
when there are multiple paths that you can utilize.

01:14:18.000 --> 01:14:24.000
So go over to R1, router, and we're in BGP Autonomous at 65,001,

01:14:24.000 --> 01:14:35.000
neighbor 192.168.255.2, remote autonomous system, 65,001.

01:14:35.000 --> 01:14:37.000
And now I'm going to say whenever I form a neighborhood

01:14:37.000 --> 01:14:43.000
or send anything to 192.168.255.2, I want to see, as you can see,

01:14:43.000 --> 01:14:44.000
we already have a malformatted message.

01:14:44.000 --> 01:14:52.000
I want to update source loopback 192, and that should solve our problem.

01:14:52.000 --> 01:15:00.000
And the reason why it was malformed, come on, clean yourself up.

01:15:00.000 --> 01:15:04.000
The reason why it's malformed is typically because of the fact that I am sending

01:15:04.000 --> 01:15:06.000
from the wrong IP and you're receiving from the wrong IP.

01:15:06.000 --> 01:15:07.000
I'm sending from the wrong IP.

01:15:07.000 --> 01:15:08.000
Okay, let me check my config here.

01:15:08.000 --> 01:15:16.000
Something's not happy with me.

01:15:16.000 --> 01:15:36.000
192.168.255.1, 192.168.255.2.

01:15:36.000 --> 01:15:51.000
Okay, show run pipe section BGP.

01:15:51.000 --> 01:16:03.000
That's strange.

01:16:03.000 --> 01:16:18.000
Do we have the right IP address on that loopback interface?

01:16:18.000 --> 01:16:33.000
192.168.255.1, okay.

01:16:33.000 --> 01:16:40.000
So we're saying neighbor 192.168.255.2, remote autonomous system, 65,001.

01:16:40.000 --> 01:16:41.000
I am 65,001.

01:16:41.000 --> 01:16:42.000
They're 65,001.

01:16:42.000 --> 01:16:43.000
That's good.

01:16:43.000 --> 01:16:48.000
192.168.255.2, update source loopback 192.

01:16:48.000 --> 01:16:51.000
Is that the loopback 192.168.255.1?

01:16:51.000 --> 01:16:52.000
Okay, that's fine.

01:16:52.000 --> 01:16:56.000
Okay, I'm starting to draw a blank on what's going on here right now.

01:16:56.000 --> 01:17:01.000
So we got 192.168.255.2, BGP, 65,001.

01:17:01.000 --> 01:17:04.000
I got the right 192.168.255.1.

01:17:05.000 --> 01:17:20.000
Okay, let me shut down that neighbor.

01:17:20.000 --> 01:17:24.000
I'm going to bring back up the other neighbor that we had shut down because I

01:17:24.000 --> 01:17:34.000
realize they're still down.

01:17:34.000 --> 01:17:54.000
It is quite possible that.

01:17:54.000 --> 01:17:56.000
Okay, so that neighbor should come back up.

01:17:56.000 --> 01:17:59.000
That's fine.

01:17:59.000 --> 01:18:03.000
Yeah, see, I don't have to do address family over on R1.

01:18:03.000 --> 01:18:07.000
So you could do classic IPv4 with.

01:18:07.000 --> 01:18:11.000
I've never had that issue before because I've done this demo many times before

01:18:11.000 --> 01:18:12.000
this exact same way.

01:18:12.000 --> 01:18:14.000
That's why I'm just trying to double check.

01:18:14.000 --> 01:18:17.000
Do I have a configuration problem?

01:18:17.000 --> 01:18:25.000
So that is the two commands we typed.

01:18:26.000 --> 01:18:51.000
So go to R1.

01:18:51.000 --> 01:19:02.000
Let's give it a try.

01:19:02.000 --> 01:19:05.000
Let's go ahead and let's do address family over here and see what happens.

01:19:32.000 --> 01:19:44.000
BGP identifier wrong.

01:19:44.000 --> 01:19:46.000
All right.

01:19:46.000 --> 01:19:50.000
I know my config is good, all right.

01:19:50.000 --> 01:19:53.000
So I'm going to bring back down that neighborhood.

01:19:53.000 --> 01:19:56.000
We're not going to keep trying to troubleshoot this because the goal here is

01:19:56.000 --> 01:19:59.000
to make sure that we totally recognize the config for the exam.

01:20:00.000 --> 01:20:02.000
I've done this demo so many times.

01:20:02.000 --> 01:20:04.000
This is the first time I've actually had this issue.

01:20:04.000 --> 01:20:09.000
I'm just wondering if it's like a bug from R1 being up so long with all the

01:20:09.000 --> 01:20:10.000
stuff I've done to it.

01:20:10.000 --> 01:20:12.000
It's just in an unstable state right now.

01:20:12.000 --> 01:20:15.000
I have had things like that happen before with other demos I've done.

01:20:15.000 --> 01:20:19.000
And so I don't want to waste everybody's time trying to troubleshoot this at

01:20:19.000 --> 01:20:23.000
this point in time when something simply as like saving my config rebooting my

01:20:23.000 --> 01:20:24.000
router solves the problem.

01:20:24.000 --> 01:20:25.000
Right.

01:20:25.000 --> 01:20:26.000
So let's not worry about that right now.

01:20:26.000 --> 01:20:30.000
Let's do a do show run pipe to section router BGP because the key here is for

01:20:30.000 --> 01:20:34.000
us to what be able to recognize the stuff right here for the certification

01:20:34.000 --> 01:20:35.000
exam.

01:20:35.000 --> 01:20:36.000
All right.

01:20:36.000 --> 01:20:37.000
So for example,

01:20:37.000 --> 01:20:39.000
make sure that when you're looking at the config,

01:20:39.000 --> 01:20:41.000
you understand what you're looking at.

01:20:41.000 --> 01:20:43.000
So I'm router to router to autonomous system,

01:20:43.000 --> 01:20:48.000
65,001 for every single neighborship you want to have,

01:20:48.000 --> 01:20:51.000
you're going to have to have a neighbor command that specifies the remote

01:20:51.000 --> 01:20:53.000
autonomous system.

01:20:53.000 --> 01:20:54.000
So in this case,

01:20:54.000 --> 01:20:59.000
we have a neighborship or a command to form a neighborship with who,

01:20:59.000 --> 01:21:03.000
with a neighbor in the same autonomous system.

01:21:03.000 --> 01:21:05.000
In this particular case at the IP address,

01:21:05.000 --> 01:21:10.000
one nine two one six eight two 55.1 down here we have,

01:21:10.000 --> 01:21:12.000
and they are what admin shutdown.

01:21:12.000 --> 01:21:14.000
So that's also good for you to know for the certification exam.

01:21:14.000 --> 01:21:15.000
So admin shutdown.

01:21:15.000 --> 01:21:17.000
So if you saw this,

01:21:17.000 --> 01:21:19.000
that would mean that you can't form a neighborship with them because they

01:21:19.000 --> 01:21:21.000
have been administratively shut down.

01:21:22.000 --> 01:21:24.000
When we look here at this command here,

01:21:24.000 --> 01:21:27.000
this is referring to the fact that when you try to form a neighborship where

01:21:27.000 --> 01:21:29.000
you send updates or any type of BGP message to one,

01:21:29.000 --> 01:21:31.000
nine two one six eight two 55.1,

01:21:31.000 --> 01:21:35.000
then you are going to source every single BGP message from the IP address

01:21:35.000 --> 01:21:39.000
of your loopback interface.

01:21:39.000 --> 01:21:42.000
This one right here is another neighborship we have,

01:21:42.000 --> 01:21:44.000
and it's with somebody in a different autonomous system.

01:21:44.000 --> 01:21:47.000
Why? Because this is different than this.

01:21:47.000 --> 01:21:49.000
So that right there is EBGP,

01:21:49.000 --> 01:21:52.000
which means what one hop away directly connected by default.

01:21:52.000 --> 01:21:56.000
So if you're further away than one router away from each other,

01:21:56.000 --> 01:21:59.000
then you're going to need the EBGP multi-hop command in that particular

01:21:59.000 --> 01:22:00.000
type of scenario.

01:22:00.000 --> 01:22:01.000
In this case,

01:22:01.000 --> 01:22:02.000
we don't need it,

01:22:02.000 --> 01:22:04.000
but I put it in there to show you that that's what that command does.

01:22:04.000 --> 01:22:05.000
Anytime you want to do authentication,

01:22:05.000 --> 01:22:08.000
it would be with what the neighbor password command.

01:22:08.000 --> 01:22:09.000
So you specify the neighbor,

01:22:09.000 --> 01:22:10.000
the address,

01:22:10.000 --> 01:22:11.000
the password command,

01:22:11.000 --> 01:22:12.000
and then the password you want to use.

01:22:12.000 --> 01:22:15.000
And it uses MD five by default folks.

01:22:16.000 --> 01:22:18.000
I know with address family IPV4,

01:22:18.000 --> 01:22:21.000
that shows up on the certification exam at a minimum.

01:22:21.000 --> 01:22:22.000
You're going to see activate there.

01:22:22.000 --> 01:22:24.000
There might be some other commands in there,

01:22:24.000 --> 01:22:25.000
but at this point in time,

01:22:25.000 --> 01:22:28.000
we haven't seen any command that specifically would live under address

01:22:28.000 --> 01:22:32.000
family IPV4 for the certification exam yet at this particular point in

01:22:32.000 --> 01:22:33.000
time.

01:22:33.000 --> 01:22:34.000
All right.

01:22:34.000 --> 01:22:35.000
So now,

01:22:35.000 --> 01:22:40.000
now what we're going to do is we're going to look at our network command.

01:22:40.000 --> 01:22:43.000
So what is the network command all about?

01:22:43.000 --> 01:22:48.000
The network command is all about advertising BGP routes.

01:22:50.000 --> 01:22:51.000
Okay.

01:22:51.000 --> 01:22:55.000
So the network command for BGP is totally different than it is for EIGRP

01:22:55.000 --> 01:22:56.000
and OSPF.

01:22:56.000 --> 01:22:59.000
The network command for EIGRP and OSPF enables the EIGRP OSPF running

01:22:59.000 --> 01:23:00.000
process on the interface.

01:23:00.000 --> 01:23:01.000
So that way there,

01:23:01.000 --> 01:23:03.000
you can form dynamic neighbor adjacencies.

01:23:03.000 --> 01:23:04.000
Okay.

01:23:04.000 --> 01:23:05.000
That's not what it does for BGP.

01:23:05.000 --> 01:23:10.000
So the network command is used for you to locally inject networks into your

01:23:11.000 --> 01:23:12.000
BGP process.

01:23:12.000 --> 01:23:16.000
And then their forces in the BGP process called the BGP table.

01:23:16.000 --> 01:23:17.000
In this case,

01:23:17.000 --> 01:23:20.000
you're going to be able to share that with other routers at that point in

01:23:20.000 --> 01:23:21.000
time.

01:23:21.000 --> 01:23:22.000
Notice it said here,

01:23:22.000 --> 01:23:24.000
the network command allows you to advertise a prefix to your neighbors.

01:23:24.000 --> 01:23:25.000
Okay.

01:23:25.000 --> 01:23:28.000
You must be exact with matching on that prefix.

01:23:28.000 --> 01:23:30.000
And if not in the routing table,

01:23:30.000 --> 01:23:31.000
it's not going to be advertised.

01:23:31.000 --> 01:23:34.000
So let me show you exactly what that means in this particular case.

01:23:34.000 --> 01:23:37.000
If you go to our over at ISPA as an example,

01:23:37.000 --> 01:23:38.000
let's type and show IP route.

01:23:38.000 --> 01:23:40.000
When we look at a routing table,

01:23:40.000 --> 01:23:43.000
we're going to see that we have all these different directly connected

01:23:43.000 --> 01:23:45.000
networks right now at this particular point in time.

01:23:45.000 --> 01:23:47.000
Now it doesn't matter if it's a directly connected network.

01:23:47.000 --> 01:23:49.000
It doesn't matter if it's a static route.

01:23:49.000 --> 01:23:51.000
It doesn't matter for the OSPF EIGP route.

01:23:51.000 --> 01:23:52.000
It doesn't matter.

01:23:52.000 --> 01:23:53.000
Okay.

01:23:53.000 --> 01:23:54.000
The fact of the matter is,

01:23:54.000 --> 01:23:56.000
is it just has to be in the routing table,

01:23:56.000 --> 01:23:57.000
anything in the routing table,

01:23:57.000 --> 01:23:58.000
no matter what it was learned,

01:23:58.000 --> 01:24:01.000
you can inject in the BGP using the network command.

01:24:01.000 --> 01:24:02.000
So if I type in,

01:24:02.000 --> 01:24:05.000
configure terminal router BGP and we're in 65,000 here.

01:24:05.000 --> 01:24:08.000
Let me type in the network command.

01:24:08.000 --> 01:24:09.000
And then,

01:24:09.000 --> 01:24:10.000
what does it ask for?

01:24:10.000 --> 01:24:11.000
It says the network number.

01:24:11.000 --> 01:24:14.000
So let me go ahead and put in this network number right here.

01:24:14.000 --> 01:24:16.000
And then it says mask.

01:24:16.000 --> 01:24:20.000
So I'm going to put in mask and then it's asking me to provide the

01:24:21.000 --> 01:24:22.000
subnet mask.

01:24:22.000 --> 01:24:23.000
And what did we see?

01:24:23.000 --> 01:24:24.000
Slash 24.

01:24:24.000 --> 01:24:26.000
So that's going to be two by five,

01:24:26.000 --> 01:24:27.000
two by five,

01:24:27.000 --> 01:24:28.000
two by five dot zero.

01:24:28.000 --> 01:24:29.000
Okay.

01:24:29.000 --> 01:24:31.000
So what I want to point out to you is that we can verify if it

01:24:31.000 --> 01:24:32.000
injected it into the BGP table,

01:24:32.000 --> 01:24:33.000
do show IP BGP.

01:24:33.000 --> 01:24:35.000
And you'll see that there's nothing in my table right now.

01:24:35.000 --> 01:24:37.000
The reason why is because this is a subnet mask.

01:24:37.000 --> 01:24:39.000
So I'm going to go ahead and put in the subnet mask.

01:24:39.000 --> 01:24:41.000
And then it's asking me for the subnet mask.

01:24:41.000 --> 01:24:42.000
And what did we see?

01:24:42.000 --> 01:24:43.000
Slash 24.

01:24:43.000 --> 01:24:45.000
So that's going to be two by five,

01:24:45.000 --> 01:24:46.000
two by five,

01:24:46.000 --> 01:24:47.000
two by five dot zero.

01:24:47.000 --> 01:24:48.000
Okay.

01:24:48.000 --> 01:24:49.000
So we're not seeing anything in our table right now.

01:24:49.000 --> 01:24:51.000
The reason why is because this is not actually an exact match to

01:24:51.000 --> 01:24:53.000
something in our routing table.

01:24:53.000 --> 01:24:54.000
It's not.

01:24:54.000 --> 01:24:56.000
And that's what I'm trying to point out to you.

01:24:56.000 --> 01:24:57.000
Okay.

01:24:57.000 --> 01:24:58.000
Most people don't realize this,

01:24:58.000 --> 01:25:00.000
but whenever you see something like this,

01:25:00.000 --> 01:25:03.000
notice how there's no source on the left-hand side.

01:25:03.000 --> 01:25:05.000
There's no source on the left-hand side.

01:25:05.000 --> 01:25:06.000
There's no source.

01:25:06.000 --> 01:25:07.000
There's no source.

01:25:07.000 --> 01:25:08.000
There's no source.

01:25:08.000 --> 01:25:10.000
Think of that as just a header,

01:25:10.000 --> 01:25:11.000
a header,

01:25:11.000 --> 01:25:12.000
a header.

01:25:12.000 --> 01:25:13.000
That's right.

01:25:13.000 --> 01:25:15.000
It's saying that anything below this until the next header is

01:25:15.000 --> 01:25:18.000
related to that network.

01:25:18.000 --> 01:25:21.000
It's related to 192.0.2.0 slash 24.

01:25:21.000 --> 01:25:24.000
It says 192.0.2.0 slash 24.

01:25:24.000 --> 01:25:29.000
192.0.2.0 slash 24 is variably subnetted into two subnets and

01:25:29.000 --> 01:25:30.000
two masks,

01:25:30.000 --> 01:25:31.000
and there they are.

01:25:31.000 --> 01:25:32.000
Okay.

01:25:32.000 --> 01:25:34.000
So that is not actually in your routing table.

01:25:34.000 --> 01:25:36.000
So if you were expecting,

01:25:36.000 --> 01:25:37.000
hey,

01:25:37.000 --> 01:25:39.000
let's advertise 192.0.2.0 slash 24,

01:25:39.000 --> 01:25:41.000
you can't because it's not actually in your routing table.

01:25:41.000 --> 01:25:45.000
It has to be something that's really in your routing table.

01:25:45.000 --> 01:25:49.000
So,

01:25:49.000 --> 01:25:50.000
for example,

01:25:50.000 --> 01:25:51.000
let's take this one right here.

01:25:51.000 --> 01:25:54.000
If we take this one and I type in something like network,

01:25:54.000 --> 01:26:01.000
and then we punch in 198.51.100.44,

01:26:01.000 --> 01:26:03.000
and it's a slash 30.

01:26:03.000 --> 01:26:04.000
What's a slash 30?

01:26:04.000 --> 01:26:07.000
255,

01:26:07.000 --> 01:26:08.000
255,

01:26:08.000 --> 01:26:10.000
255,

01:26:10.000 --> 01:26:11.000
255,

01:26:11.000 --> 01:26:14.000
252.

01:26:14.000 --> 01:26:16.000
Now if we type in show IP BGP,

01:26:16.000 --> 01:26:23.000
you're going to see it's actually in the BGP table.

01:26:23.000 --> 01:26:28.000
And the next top is 0000 because I'm the one who brought it in to BGP.

01:26:28.000 --> 01:26:29.000
It was me.

01:26:29.000 --> 01:26:30.000
Look at the AS path.

01:26:30.000 --> 01:26:32.000
The AS path is blank.

01:26:32.000 --> 01:26:33.000
Why?

01:26:33.000 --> 01:26:37.000
Because I am the autonomous system that owns this.

01:26:37.000 --> 01:26:38.000
I own it.

01:26:38.000 --> 01:26:39.000
I know it's me.

01:26:39.000 --> 01:26:41.000
So I don't have to put that information in there right now.

01:26:41.000 --> 01:26:43.000
I only put the information in once I send it.

01:26:43.000 --> 01:26:45.000
So now if we go into something like R2,

01:26:45.000 --> 01:26:47.000
you're going to see this is now learned by R2.

01:26:47.000 --> 01:26:49.000
R2 is going to have this,

01:26:49.000 --> 01:26:53.000
but you're also going to see the autonomous system number here now,

01:26:53.000 --> 01:26:55.000
because when I generate my BGP message,

01:26:55.000 --> 01:26:56.000
the ISP,

01:26:56.000 --> 01:26:57.000
and sends it out,

01:26:57.000 --> 01:27:02.000
it says 198.51.100.44 slash 30 with all other information.

01:27:02.000 --> 01:27:05.000
The next hop is going to be the next hop IP address of the ISP router.

01:27:06.000 --> 01:27:09.000
That is going to be the autonomous system over the ISP router.

01:27:09.000 --> 01:27:10.000
So if we go over to R2 now,

01:27:10.000 --> 01:27:12.000
take a peek at that,

01:27:12.000 --> 01:27:14.000
do show IP BGP.

01:27:14.000 --> 01:27:15.000
And there you go.

01:27:19.000 --> 01:27:20.000
Let's go back to the ISP,

01:27:20.000 --> 01:27:23.000
and let's grab another thing that we have in our routing table.

01:27:23.000 --> 01:27:24.000
So, for example,

01:27:24.000 --> 01:27:29.000
we have 8.8.8.8 slash 32 in this case that I have.

01:27:29.000 --> 01:27:34.000
So network 8.8.8.8 slash 32.

01:27:34.000 --> 01:27:35.000
So it's going to be masked,

01:27:35.000 --> 01:27:37.000
and it's going to be 255.255.

01:27:41.000 --> 01:27:42.000
Be careful.

01:27:42.000 --> 01:27:44.000
For example, if I did this by accident,

01:27:44.000 --> 01:27:45.000
not going to work.

01:27:45.000 --> 01:27:47.000
Take a look at the BGP table.

01:27:47.000 --> 01:27:48.000
Not in there.

01:27:48.000 --> 01:27:49.000
Why?

01:27:49.000 --> 01:27:50.000
Because that doesn't exist in my routing table.

01:27:50.000 --> 01:27:52.000
So pay attention on the exam for that.

01:27:52.000 --> 01:27:56.000
Make sure if it's a scenario where you're troubleshooting a BGP route,

01:27:56.000 --> 01:28:01.000
double check to make sure that the network command matches the exact address

01:28:01.000 --> 01:28:02.000
that's in the table,

01:28:02.000 --> 01:28:03.000
routing table.

01:28:03.000 --> 01:28:05.000
If the address is not in the routing table,

01:28:05.000 --> 01:28:07.000
find out why that is.

01:28:07.000 --> 01:28:12.000
Maybe it's because OSPF is improperly advertising that route.

01:28:12.000 --> 01:28:15.000
Or maybe the static route is not being installed in the routing table.

01:28:15.000 --> 01:28:20.000
Or maybe the interface with a directly connected route is not up, up.

01:28:20.000 --> 01:28:22.000
You see how all those little things matter?

01:28:22.000 --> 01:28:25.000
How do those routes get in the routing table?

01:28:25.000 --> 01:28:26.000
That's number one.

01:28:26.000 --> 01:28:28.000
Because if there's a network command,

01:28:28.000 --> 01:28:29.000
and it's correct,

01:28:30.000 --> 01:28:32.000
and router 2 is not learning that route,

01:28:32.000 --> 01:28:35.000
well, maybe it's not a BGP problem.

01:28:35.000 --> 01:28:39.000
Maybe it's a problem related to the fact that that route is not in the routing

01:28:39.000 --> 01:28:40.000
table.

01:28:40.000 --> 01:28:41.000
Why is that?

01:28:41.000 --> 01:28:44.000
Now you're troubleshooting the underlying reason why the route's not in the

01:28:44.000 --> 01:28:45.000
routing table.

01:28:45.000 --> 01:28:47.000
So it may start out as a BGP problem on the exam,

01:28:47.000 --> 01:28:49.000
but it ultimately leads to what?

01:28:49.000 --> 01:28:51.000
Maybe a problem with an interface not being up, up.

01:28:51.000 --> 01:28:53.000
So always be mindful of that.

01:28:53.000 --> 01:28:56.000
When you're in the CCNP level of training and certifications,

01:28:56.000 --> 01:28:58.000
you could be focused primarily on BGP.

01:28:58.000 --> 01:29:01.000
But in the end, why is that not happening?

01:29:01.000 --> 01:29:06.000
Is what you're trying to get at.

01:29:06.000 --> 01:29:08.000
So now we look, and you'll see that it's also in the table now.

01:29:08.000 --> 01:29:11.000
So if you go over to R2, R2 is going to learn about it.

01:29:11.000 --> 01:29:13.000
And there we go.

01:29:13.000 --> 01:29:19.000
So let's take a look here at address family IPV4 Unicast over on router

01:29:19.000 --> 01:29:20.000
number 2.

01:29:20.000 --> 01:29:21.000
Because in this case,

01:29:21.000 --> 01:29:25.000
you'll see that the network command exists for IPV4 here.

01:29:25.000 --> 01:29:28.000
So here's an example of using a command in the address family configuration

01:29:28.000 --> 01:29:29.000
mode.

01:29:29.000 --> 01:29:31.000
Let me type in do show IP route.

01:29:31.000 --> 01:29:33.000
And let's see what I have here that we can go ahead and use.

01:29:33.000 --> 01:29:36.000
Look, we have a BGP route and a routing table now.

01:29:36.000 --> 01:29:38.000
Let's go down a little further.

01:29:38.000 --> 01:29:40.000
We should see the other BGP route and a routing table.

01:29:40.000 --> 01:29:43.000
So let's have some fun with this and let's just go ahead.

01:29:43.000 --> 01:29:46.000
And I know these are, I know these are,

01:29:46.000 --> 01:29:52.000
whatchamacallit, private addresses, but that's okay.

01:29:52.000 --> 01:29:54.000
For our example, that's perfectly fine.

01:29:54.000 --> 01:29:58.000
So let's go ahead and type in network.

01:29:58.000 --> 01:30:04.000
The address, the mask, 255.255.255.0.

01:30:04.000 --> 01:30:06.000
Do show IP route.

01:30:06.000 --> 01:30:07.000
Oops, not route.

01:30:07.000 --> 01:30:12.000
Show IP BGP.

01:30:12.000 --> 01:30:15.000
And you'll see here that I've injected myself into this.

01:30:15.000 --> 01:30:17.000
Now look at the next hop.

01:30:17.000 --> 01:30:19.000
The next hop, even though I use the network command,

01:30:19.000 --> 01:30:22.000
notice the next hop is somewhere else because I don't own that.

01:30:22.000 --> 01:30:28.000
So if this is not a route that is directly connected to me,

01:30:28.000 --> 01:30:32.000
then I will specify the actual next hop that I need in order to get there.

01:30:32.000 --> 01:30:35.000
But now when the ISP gets it, who's the next hop?

01:30:35.000 --> 01:30:37.000
The next hop is R2.

01:30:37.000 --> 01:30:42.000
See, R2's address is there, which is what we'd expect because we want to

01:30:42.000 --> 01:30:46.000
make sure that ISP router knows that it has to go to this next hop IP

01:30:46.000 --> 01:30:51.000
address in order to get to the particular destination, 10.0.0.24.

01:30:51.000 --> 01:30:55.000
So, folks, that's your network command when it's all said and done.

01:30:55.000 --> 01:30:58.000
Now, if R2 was working in my particular case, which it's not,

01:30:58.000 --> 01:31:00.000
I can't get that neighborhood running between R1 and 2.

01:31:00.000 --> 01:31:06.000
I'll try to get it sorted out during our break when we have it.

01:31:06.000 --> 01:31:13.000
But in that particular case, R1 would be learning through IPGV all the

01:31:13.000 --> 01:31:16.000
information that is coming over from R2.

01:31:16.000 --> 01:31:19.000
So R2 would be learning from ISPA and then sharing that information over

01:31:19.000 --> 01:31:21.000
because of how we have our neighborhood.

01:31:21.000 --> 01:31:38.000
So we've got an EBGP here and we have an IBGP here.

01:31:38.000 --> 01:31:39.000
All right, and a few final,

01:31:39.000 --> 01:31:44.000
final nuggets of information before we wrap up this overview,

01:31:44.000 --> 01:31:47.000
BGP configuration and verification of BGP.

01:31:47.000 --> 01:31:50.000
So look at this scenario here.

01:31:50.000 --> 01:31:53.000
I have to introduce this to you right now.

01:31:53.000 --> 01:31:56.000
I'm not going to demo it live because it's going to require a lot more

01:31:56.000 --> 01:31:58.000
configuration to accomplish this.

01:31:58.000 --> 01:32:02.000
But think of a scenario, let's say,

01:32:02.000 --> 01:32:08.000
where this is your HQ and this is your branch office.

01:32:08.000 --> 01:32:14.000
Notice how you are using the same autonomous system number in HQ and the

01:32:14.000 --> 01:32:19.000
same autonomous system number in branch, which is perfectly fine.

01:32:19.000 --> 01:32:24.000
What you need to recognize is that in this scenario,

01:32:24.000 --> 01:32:31.000
I have an EBGP neighborhood here and I have an EBGP neighborhood here.

01:32:31.000 --> 01:32:33.000
That's what we have.

01:32:33.000 --> 01:32:36.000
There's no neighborhood directly between those two different autonomous

01:32:36.000 --> 01:32:39.000
systems.

01:32:40.000 --> 01:32:44.000
So I'm advertising my public networks up this way.

01:32:44.000 --> 01:32:47.000
The ISP is getting them.

01:32:47.000 --> 01:32:51.000
And when the ISP gets it, what's going to happen here?

01:32:51.000 --> 01:33:01.000
Let's say the network, let's just pretend the network over here is 192.0.2.0

01:33:01.000 --> 01:33:02.000
slash 24.

01:33:02.000 --> 01:33:06.000
Let's just pretend that that is the network, the public network we have.

01:33:06.000 --> 01:33:14.000
So when the ISP gets it, it learns about it as 192.0.2.0 slash 24 via

01:33:14.000 --> 01:33:19.000
autonomous system number 65001.

01:33:19.000 --> 01:33:23.000
And now when it shares it down here using EBGP,

01:33:24.000 --> 01:33:38.000
then when branch gets it, branch uses 192.0.2.0 slash 24 via AS6500 comma

01:33:38.000 --> 01:33:41.000
65001.

01:33:41.000 --> 01:33:44.000
Okay, you see this one right here, this autonomous system number there,

01:33:44.000 --> 01:33:46.000
65001?

01:33:46.000 --> 01:33:49.000
That conflicts with this one.

01:33:49.000 --> 01:34:00.000
So with BGP, if you ever receive a network and in the attributes,

01:34:00.000 --> 01:34:04.000
you see your very own autonomous system number,

01:34:04.000 --> 01:34:08.000
you will automatically drop that information.

01:34:08.000 --> 01:34:27.000
Okay.

01:34:27.000 --> 01:34:29.000
So this is a problem, isn't it?

01:34:29.000 --> 01:34:32.000
Because now I'm not going to learn about the public networks that HQ has

01:34:32.000 --> 01:34:36.000
that I need to know.

01:34:37.000 --> 01:34:41.000
We can override this behavior with the allow ASN option.

01:34:41.000 --> 01:34:46.000
Allows you to receive and keep routes even if your AS number is already in

01:34:46.000 --> 01:34:47.000
the path.

01:34:47.000 --> 01:35:01.000
That's what this would allow us to do.

01:35:01.000 --> 01:35:08.000
So, for example, what we'd have to do is we'd have to go over to both R2

01:35:08.000 --> 01:35:09.000
and branch.

01:35:09.000 --> 01:35:14.000
That's where we do this configuration, R2 and branch.

01:35:14.000 --> 01:35:17.000
And so just think about the fact that on R2,

01:35:17.000 --> 01:35:23.000
you would have typed in neighbor 203.0.113.89,

01:35:23.000 --> 01:35:27.000
remote autonomous system 65,000.

01:35:27.000 --> 01:35:30.000
In addition, now you have to add another command.

01:35:30.000 --> 01:35:32.000
And what's that command going to be?

01:35:32.000 --> 01:35:41.000
It's going to be neighbor 203.0.113.89 allow ASN.

01:35:41.000 --> 01:35:44.000
Allow ASN.

01:35:44.000 --> 01:35:59.000
So, for example, wrong configuration mode, probably.

01:35:59.000 --> 01:36:17.000
Nope, there it is.

01:36:17.000 --> 01:36:19.000
All right, so there's just another command to keep in mind for the

01:36:19.000 --> 01:36:21.000
certification exam.

01:36:22.000 --> 01:36:30.000
So any scenario whereby you are going to be required to receive routes from

01:36:30.000 --> 01:36:34.000
your own autonomous system over the internet,

01:36:34.000 --> 01:36:38.000
you're going to have to make sure that you have that command that allows ASN

01:36:38.000 --> 01:36:40.000
from that directly connected neighbor.

01:36:40.000 --> 01:36:42.000
So we'd have to go over to branch as well and do the same thing.

01:36:42.000 --> 01:36:47.000
So on branch, maybe we typed in neighbor 198.51.100.45,

01:36:47.000 --> 01:36:49.000
remote ASN 65,000.

01:36:49.000 --> 01:36:51.000
So that's the neighborship for the eBGP neighborship.

01:36:51.000 --> 01:37:01.000
And then we type in neighbor 198.51.100.45 allow AS-IN.

01:37:01.000 --> 01:37:07.000
Now, there's another option we have here, and that is AS override.

01:37:07.000 --> 01:37:10.000
Allows you to remove an autonomous system number and replace it with your

01:37:10.000 --> 01:37:11.000
own autonomous system number.

01:37:11.000 --> 01:37:17.000
So remember when I was talking about the ability to use private autonomous

01:37:17.000 --> 01:37:18.000
system numbers?

01:37:18.000 --> 01:37:23.000
And then you piggyback on top of your ISP's autonomous system number.

01:37:23.000 --> 01:37:27.000
Let's see if I still have that diagram up that we did before.

01:37:27.000 --> 01:37:29.000
So where was that?

01:37:29.000 --> 01:37:30.000
I think it was this page.

01:37:30.000 --> 01:37:31.000
Yeah, it's right there.

01:37:31.000 --> 01:37:32.000
Good.

01:37:32.000 --> 01:37:33.000
And it's still there.

01:37:33.000 --> 01:37:36.000
So this is what would happen if you were public, right?

01:37:36.000 --> 01:37:38.000
So if you had a public autonomous system number,

01:37:38.000 --> 01:37:42.000
there's my autonomous system number, and then the ISP adds onto that list,

01:37:42.000 --> 01:37:43.000
and away you go.

01:37:43.000 --> 01:37:48.000
And remember we said, what if we were like 65,145?

01:37:48.000 --> 01:37:56.000
Well, what would happen here is that you would have 65,145, 65,145,

01:37:56.000 --> 01:37:58.000
and then that would get stripped, okay?

01:37:58.000 --> 01:38:04.000
Those would get stripped, and it would be replaced with just your ISP's

01:38:04.000 --> 01:38:07.000
autonomous system number.

01:38:07.000 --> 01:38:12.000
So that way there, the Internet doesn't see that private autonomous system

01:38:12.000 --> 01:38:13.000
number.

01:38:13.000 --> 01:38:18.000
So that's essentially what's going on here in this particular case.

01:38:18.000 --> 01:38:25.000
So what would happen here is that any time I learn now from this autonomous

01:38:25.000 --> 01:38:33.000
system, the ISP could have set up here neighbor 20301391,

01:38:33.000 --> 01:38:38.000
so my router's IP address, remote autonomous system 65,001.

01:38:38.000 --> 01:38:43.000
Then they would also have the command 20301391 AS override,

01:38:43.000 --> 01:38:46.000
which means allow you to remove the AS number

01:38:46.000 --> 01:38:49.000
and replace it with your own AS number instead.

01:38:49.000 --> 01:38:55.000
So if the ISP did that for incoming here and did that for incoming here,

01:38:55.000 --> 01:38:57.000
then when that information's shared there,

01:38:57.000 --> 01:38:59.000
this is going to be stripped out of it.

01:38:59.000 --> 01:39:02.000
And when this information that's coming in this way gets shared down here,

01:39:02.000 --> 01:39:05.000
then that information's stripped out of it.

01:39:05.000 --> 01:39:10.000
So now your branch doesn't see that it came from here specifically.

01:39:10.000 --> 01:39:15.000
It thinks it came directly from the ISP, and HQ doesn't see 65,001 specifically.

01:39:15.000 --> 01:39:17.000
It thinks it all came from the ISP.

01:39:17.000 --> 01:39:21.000
So that would be AS override.

01:39:21.000 --> 01:39:28.000
So if we look at our config, allow AS in was that one,

01:39:28.000 --> 01:39:31.000
and then the other one would be AS override.

01:39:31.000 --> 01:39:36.000
Override matching AS number while sending an update.

01:39:36.000 --> 01:39:37.000
All right?

01:39:37.000 --> 01:39:41.000
So that's what I want you to know to get ready for the certification exam,

01:39:41.000 --> 01:39:43.000
for configuration and verification.

01:39:43.000 --> 01:39:46.000
So now you know how to create your neighbors, neighbor command.

01:39:46.000 --> 01:39:49.000
You know, a bunch of little added things I added to that conversation

01:39:49.000 --> 01:39:51.000
so you can pick things out of a lineup on the exam,

01:39:51.000 --> 01:39:53.000
and you know the network command.

01:39:53.000 --> 01:39:55.000
You know the states of BGP.

01:39:55.000 --> 01:39:57.000
You know the messages for BGP.

01:39:58.000 --> 01:40:02.000
You know AS override, and you know allow AS in.

01:40:02.000 --> 01:40:04.000
All right, make sure you know all of those for the exam.