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Well, it's time to see this configuration in action.

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We need to log into our iOS XC devices, log into this lab space, and actually

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do the configurations

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for VRFs and GRE tunnels.

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And so what we're going to do here in this lab is just start off by looking

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just one at

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a time.

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We're going to do VRFs in this session.

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In the next video, we'll take a look at the GRE tunnels.

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And then in the challenge, we're going to find that we're going to combine the

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two together.

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We're going to have to build an environment from scratch, including an underlay
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We're going to have to build an environment from scratch, including an underlay

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VRF.

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So that's actually pretty cool how that all comes together.

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For now, let's go ahead and explore our configuration commands.

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And I would encourage you also to go ahead and maybe pull up the lab

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environment that

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is included in the skill down below.

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And during these first two videos, play around with the configuration, make

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sure we're comfortable

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with setting it all up and then reset that lab environment for the lab

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challenge.

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Because when we do the lab challenge, we're going to want a fresh, basically

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how it loads,

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we want that fresh configuration in place when we begin the lab challenge.
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we want that fresh configuration in place when we begin the lab challenge.

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But just configuring these commands as we go along together would be a very

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good way

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to make sure that we are grasping it and locking it in.

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So our topology for this video specifically, again, we're using the same lab

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environment

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for all of it, but we're just going to use a few different devices each time.

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For this one, we're going to have, let's see here, we've got router 3

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connecting into

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router 1, then connecting to router 2.
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router 1, then connecting to router 2.

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And what we're going to do is we're going to configure VRFs on both sides.

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So we'll do VRF, since this is 1 and 3, we'll do 13 and VRF 12 on the right.

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So we're going to effectively carve router 1 up into two different VRFs.

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Now router 3 and router 2 don't need to be VRF aware, if they exist entirely

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within

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one VRF within one layer 3 environment, then we don't need to worry about

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configuring

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it on those devices.

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It's the devices in the middle that have multiple VRFs.
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It's the devices in the middle that have multiple VRFs.

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That point we need to be very intentional with our VRF definitions as well as

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our interface

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assignments.

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So keep in mind what we're accomplishing with VRFs.

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VRFs are carving a layer 3 device like a router up into multiple layer 3

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domains in the same

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way that we do that with VLANs and layer 2 switches.

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Now in this environment, from a subnet and routing perspective, we do have OSPF

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running

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throughout this entire space.

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We're going to see that we need to modify OSPF here on this router in order to
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We're going to see that we need to modify OSPF here on this router in order to

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make it

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work with VRFs.

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And from a subnet perspective, we have 10.0.13.0/24 with .3 for router 3, .1

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for router 1,

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and then over here 10.0.23.0/24 once again, .1 and this time .2 for router 2.

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So hopefully that gives us all of the configuration information we need just to
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So hopefully that gives us all of the configuration information we need just to

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kind of poke around

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with VRFs here.

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So let's go ahead and get onto router 1 here.

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Yeah, well, I don't have a router 1.

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So router 1 and we're going to start by entering global configuration mode and

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we have to begin

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with defining the VRFs.

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And we literally use the word definition for defining here.

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So VRF definition and then I'll say VRF 12.

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Now keep in mind, VLANs have to be a number whereas VRFs can be a name.

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So I could just call this 12, I could use numbers in my VRF naming scheme, but
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So I could just call this 12, I could use numbers in my VRF naming scheme, but

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usually

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it's better to avoid that and just feels a little cleaner to have something

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like VRF

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in front of it and that way we know for sure what's going on.

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So we enter into this sub configuration prompt here, this VRF subconfig.

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And we have to enable this VRF with an address family.

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The address family is going to allow me to enable, for example, IPv4, IPv6.
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The address family is going to allow me to enable, for example, IPv4, IPv6.

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And then on some platforms, not this one, but on some platforms we'll see that

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we can

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individually enable unicast and multicast routing.

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For now, we'll just hit enter and even on those platforms we can just hit enter

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and

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enable both of those.

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So I just want to prepare you for in case you do a question mark in your own

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lab environment

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and you see more options there.

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Now if you are running on older lab hardware, I know if you're like me, in my

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lab environment,

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I've got some pretty old routers running.

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And Cisco at some point changed the syntax for this.
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And Cisco at some point changed the syntax for this.

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And I will say relatively recently, I mean not like a year or two ago, but also

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not 15

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years ago.

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And so they changed this concept over to VRF definition and VRF forwarding as

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we're about

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to see.

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Whereas before it just simply used to be IPVRF.

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All of the commands started with IP and then you saw VRF.

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So if you're configuring this on an old 2900 router, for example, then you

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might type

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VRF definition and it doesn't work.

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Just type IPVRF and understand that the syntax has changed.
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Just type IPVRF and understand that the syntax has changed.

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But in the modern era and modern equipment, it's all going to be VRF definition

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and a

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VRF forwarding rather than IPVRF forwarding.

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So once we've configured the VRF, we can go ahead and apply it to our interface

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.

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And oh, you know, let's since we're here, we might as well go ahead and just

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create the

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other VRF as well.

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So VRF definition, VRF 13, and once again, address family IP before.
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So VRF definition, VRF 13, and once again, address family IP before.

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All right.

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So now we can apply our VRF to the interfaces.

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Now, if I look at these interfaces and the interfaces here should be gig one

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zero and

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two zero, I believe one zero and two zero.

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Okay.

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Yes, it is.

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So when we look at these interfaces, we already have IP addressing.

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We have 10 dot zero dot 13 dot one, which is right here.

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And then we also have 10 dot zero dot 12 dot one, which would be on the other
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And then we also have 10 dot zero dot 12 dot one, which would be on the other

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side right

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there.

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So these interfaces are going to need to be placed into the VRF or into these

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new VRFs.

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The thing about this is we might already have an interface in VRF 13 that

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happens to

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have the 10 dot zero dot 13 dot one subnet or really address at that point.

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So remember, VRFs allow us to have duplicate IP addresses across the different

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VRFs.

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So it's not a duplicates.
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So it's not a duplicates.

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It's not technically a duplicate address if it doesn't exist in the same VRF

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because

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different VRFs are truly different routing spaces.

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So I could have 10 dot zero dot 13 dot one in every single one of my VRFs.

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I could apply it to VRF 13 VRF 12 and the default VRF.

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Never forget about that.

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So we've got three VRFs running on router one right now.

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The thing is is that if I'm going to place an interface into a new VRF Cisco

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wants to

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prevent the situation where we have an IP address in this VRF and it works, but
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prevent the situation where we have an IP address in this VRF and it works, but

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that

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that IP address already exists in the new VRF.

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And so we put it in there, it causes the conflict, that would be bad.

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So just to make sure we are starting with a fresh slate, so to speak, Cisco is

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going

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to wipe the IP address off that interface when we change it.

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And so what we're going to find here is that we will have to reconfigure the IP

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addresses.

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So let's go ahead and do that.

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And running a show run like this allows us to very quickly restore the IP
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And running a show run like this allows us to very quickly restore the IP

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addresses.

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We're not going to need the IPV6 addresses, so we won't worry about those.

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Let me get on to interface gig one zero to start with.

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And the command for this is VRF forwarding.

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And again, on legacy platforms, we put an IP in the front of that IP VRF

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forwarding.

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But on modern platforms, it's VRF forwarding.

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And then I can say VRF.

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And let's see here.

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It is 12.1, which is over on the right.

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And so I said 23.0.
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And so I said 23.0.

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How about that?

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So that's a little bit wrong.

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That should actually be 12.

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There we go.

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That's more correct.

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All right, so now we'll say VRF 12.

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And we see that the IP addresses have been removed and OSPF has lost its IP

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address.

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So it has gone down that neighbor relationship between R1 and R2.

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So from here, I'm going to restore the IP address.
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So from here, I'm going to restore the IP address.

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And again, I can just kind of scroll up, grab the configuration, paste it in,

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and we're

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good.

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So then I can do interface gig two zero.

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Same thing, except this time it's going to be VRF forwarding VRF 13.

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IP addresses are removed.

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Scroll back up a little bit, grab that IP address command, and we've restored

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the IP

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addresses.

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So at this point, if I run those same commands, show run interface gig one zero
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So at this point, if I run those same commands, show run interface gig one zero

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, and then

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two zero, we should now see that we're part of VRF 12 on the right.

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12.1 address is still there.

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So that's good.

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Well, thereafter, I put it back on.

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And then VRF 13 here on the left, 13.1 pointing out towards router three.

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So I should be able to do my ping commands.

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Now, again, if I were to say, even if I just ping my own address, let's see, 10

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.0.13.1,

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we're going to find that this ping command is no longer working.
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we're going to find that this ping command is no longer working.

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And the reason for that is because the ping command assumes the default VRF.

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I have to now specify which VRF I want to ping.

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So I have to say ping VRF, and then I could say VRF 12.

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Let's do that one first.

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And over on the 12 side, it should be 10.0.12.2.

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So that should be router two.

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And once our works, there we go.

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And then also VRF 13, 10.0.13.3 should be router three.
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And then also VRF 13, 10.0.13.3 should be router three.

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And there we go.

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So that's great.

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The IP addresses are working.

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I can ping if I do a show IP OSPF neighbors, we are still a big blank here.

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So why didn't OSPF come up?

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Well, if I do a show run and look at the OSPF configuration, we are going to

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find that

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we actually need to replace this configuration because router OSPF 1 assumes

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the default VRF
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the default VRF

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as well.

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So we're going to say no router OSPF 1, and then we're going to make OSPF aware

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.

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I'm going to use the same process ID.

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It doesn't matter which one I pick here.

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But when I run my question mark here, we'll see I can specify a VRF.

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So if, again, we're creating a brand new routing domain.

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If I'm creating a brand new routing domain, I'm going to need the routing

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protocols to

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exist only within that domain, within that layer three VRF.
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exist only within that domain, within that layer three VRF.

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So if router OSPF 1 goes to the default VRF, then I need to create a different

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process

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of routing process that works in the other VRF.

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So in this case, I was able to remove OSPF 1.

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In the case I couldn't remove it, I might do something like router OSPF 12 and

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then

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VRF for VRF 12.

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But since I got rid of OSPF 1, I can just add this in.

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Let's, we're going to have to create two different routing processes here for

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the two different

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VRFs.

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So let's just go ahead and call this OSPF 12 now.
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So let's just go ahead and call this OSPF 12 now.

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I think about it and then we'll say VRF 12.

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And then I can put this network statement back in.

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So network 10, 0, 12.1, all 0 is white mask, really just targets that specific

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IP address.

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And there we go.

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We've got our OSPF neighbor or adjacency really back with R2.

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Now let's do the same thing.

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On the other side, on the left side of that diagram, OSPF 13, VRF 13.

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And then we will grab that network statement for that subnet.
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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And then we will grab that network statement for that subnet.

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And there we go.

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So now we have OSPF, we should see some OSPF routes here.

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If I do a show IP route, OSPF, look at that, no OSPF routes.

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So what went wrong here?

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Well, what went wrong is simply that show IP route OSPF is assuming the default

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VRF again.

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How about that?

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Show IP route VRF and then specify the VRF and then I can specify a routing
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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Show IP route VRF and then specify the VRF and then I can specify a routing

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protocol

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like OSPF.

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So there we go.

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I've got an OSPF route in VRF 12.

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I could do the same thing for VRF 13.

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And it looks like I don't actually have any routes coming from there.

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But if I do a show IP OSPF neighbor and now we do see, I'm be very careful

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about this

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command.

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And I see that we have these two adjacencies established.

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It does not specify the VRF.
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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It does not specify the VRF.

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So we just happen to not be getting any routes from router 13.

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And that's fine in this situation.

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We're not actually advertising anything.

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It's what it comes down to.

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So what's the takeaway here?

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Well, what we need to keep in mind is that when we establish different layer

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three domains

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with using VRFs, it changes the way our configurations work.

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We have to not only create the VRF, we have to place it onto interfaces at WIPE

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's IP address.

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I have to put the IP address back in there.
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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I have to put the IP address back in there.

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I can now have that IP address on different interfaces on the same device so

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long as those

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interfaces are in different VRFs.

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Every layer three interface, whether that's a sub interface, a physical

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interface, a VLAN

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interface belongs to a VRF.

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And by default, it's part of the default VRF.

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So when we run commands like ping and show IP route and trace route and all of

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these,

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we're going to assume the default VRF.

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And so as soon as I start using VRFs, I have to start specifying which VRF I
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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And so as soon as I start using VRFs, I have to start specifying which VRF I

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want to run

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those commands in.

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So again, VRFs carve our layer three device up into multiple layer three

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domains, and

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it changes the way that I have to use the commands because now I have to think

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about

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which layer three domain I want to operate in.