WEBVTT 1 00:00.000 --> 00:04.720 So when it comes down to a device that is acting as a layer 3 IP router, 2 00:04.720 --> 00:10.200 it really boils down to three basic ways that a router can learn how to make a 3 00:10.200 --> 00:11.160 forwarding decision. 4 00:11.160 --> 00:14.200 Number one, it can have a directly connected network. 5 00:14.200 --> 00:17.400 Another example could be our Gateway Zero, our services router here, 6 00:17.400 --> 00:19.480 that is also directly connected to that segment, 7 00:19.480 --> 00:23.280 and also our Tier Zero Gateway is also directly connected to this segment and 8 00:23.280 --> 00:24.000 that segment, 9 00:24.000 --> 00:27.280 and each of those segments is associated with an IP subnet, 10 00:27.280 --> 00:29.720 and as a result, those directly connected IP networks 11 00:29.720 --> 00:31.440 would become part of the routing table. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 11 00:29.720 --> 00:31.440 would become part of the routing table. 12 00:31.440 --> 00:34.000 So that's one of our options for populating a routing table. 13 00:34.000 --> 00:37.680 Another option is to go ahead and have a static route configured. 14 00:37.680 --> 00:40.760 And think of a static route like specific instructions that you and I have to 15 00:40.760 --> 00:42.120 manually configure 16 00:42.120 --> 00:44.880 on a router to tell it how to make a forwarding decision. 17 00:44.880 --> 00:48.400 So for example, if we came in manually and we created a default route here, 18 00:48.400 --> 00:52.640 the next top is over here at the IP address of this external router, 19 00:52.640 --> 00:54.320 that would be an example of a static route, 20 00:54.320 --> 00:58.720 or if we manually went in and specified how to reach the 1010 or 1020 subnets, 21 00:58.720 --> 01:01.000 again, those would be examples of static routes. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 21 00:58.720 --> 01:01.000 again, those would be examples of static routes. 22 01:01.000 --> 01:04.560 However, in the world of NSX, we have a much more elegant solution that is at 23 01:04.560 --> 01:05.760 our Tier 1 gateways. 24 01:05.760 --> 01:09.420 We simply check the box, it says, "Please advertise those directly connected 25 01:09.420 --> 01:09.840 networks, 26 01:09.840 --> 01:13.340 and as a result, our Tier Zero Gateway knows about those without having to put 27 01:13.340 --> 01:14.440 in static routes." 28 01:14.440 --> 01:17.290 And then the third option regarding training a router on how to make a 29 01:17.290 --> 01:18.240 forwarding decision 30 01:18.240 --> 01:20.400 is to use a dynamic routing protocol. 31 01:20.400 --> 01:23.720 And although there are several different dynamic routing protocols out there, 32 01:23.720 --> 01:26.680 the ones that are supported by NSX include OSPF, 33 01:26.680 --> 01:30.920 which we covered in a previous skill, and also border gateway protocol, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 33 01:26.680 --> 01:30.920 which we covered in a previous skill, and also border gateway protocol, 34 01:30.920 --> 01:32.920 which goes by the acronym of BGP. 35 01:32.920 --> 01:37.260 So in this skill, we're going to focus on setting up BGP between our Tier Zero 36 01:37.260 --> 01:37.880 Gateway 37 01:37.880 --> 01:41.400 and an external router who's also running border gateway protocol. 38 01:41.400 --> 01:44.540 So let me clean that up a little bit, and let's talk about some use cases for B 39 01:44.540 --> 01:45.800 GP in general. 40 01:45.800 --> 01:49.560 One of the major use cases for BGP is on the Internet. 41 01:49.560 --> 01:52.200 So let's imagine we have several service providers out there, 42 01:52.200 --> 01:56.120 which we do on the public Internet today, and I'll just draw three of them. 43 01:56.120 --> 01:58.120 So let's say this is a service provider A, 44 01:58.120 --> 02:02.120 and this one is service provider B, and over here, this is going to be service WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 44 01:58.120 --> 02:02.120 and this one is service provider B, and over here, this is going to be service 45 02:02.120 --> 02:02.760 provider C. 46 02:02.760 --> 02:06.350 And let's go ahead and add a whole bunch of routers to each of those service 47 02:06.350 --> 02:07.000 providers. 48 02:07.000 --> 02:09.240 So those little green circles represent routers, 49 02:09.240 --> 02:11.880 and then it's very likely we're going to have a bunch of connections between 50 02:11.880 --> 02:12.760 those routers 51 02:12.760 --> 02:15.160 inside of a service provider network. 52 02:15.160 --> 02:16.840 We'll put some fault tolerance there. 53 02:16.840 --> 02:20.250 We'll put some connections here as well, maybe a little fault tolerance there 54 02:20.250 --> 02:20.680 as well. 55 02:20.680 --> 02:24.540 And also here for service provider C, we'll put some connections between the 56 02:24.540 --> 02:24.920 routers, 57 02:24.920 --> 02:26.760 and maybe one like that, one like that. 58 02:26.760 --> 02:32.040 So let's imagine the service provider A has 10,000 routes that it's responsible WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 58 02:26.760 --> 02:32.040 So let's imagine the service provider A has 10,000 routes that it's responsible 59 02:32.040 --> 02:32.680 for, 60 02:32.680 --> 02:38.650 and service provider B has 20,000 routes, and service provider C has 30,000 61 02:38.650 --> 02:39.320 routes. 62 02:39.320 --> 02:41.160 Now, when we're dealing with that many routes, 63 02:41.160 --> 02:44.680 and if we multiply that by many more service providers and many more routes, 64 02:44.680 --> 02:49.080 we literally have hundreds of thousands of routes out there on the Internet. 65 02:49.080 --> 02:51.080 And when we start looking at large number of routes, 66 02:51.080 --> 02:54.920 and so on the Internet today regarding just IP version four, we have hundreds 67 02:54.920 --> 02:56.280 of thousands of routes. 68 02:56.280 --> 02:59.720 And then for IPV six, we have hundreds of thousands more routes. 69 02:59.720 --> 03:03.000 So when dealing with large quantities of routes, we need a dynamic routing WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 69 02:59.720 --> 03:03.000 So when dealing with large quantities of routes, we need a dynamic routing 70 03:03.000 --> 03:03.560 protocol 71 03:03.560 --> 03:05.560 that can handle that quantity. 72 03:05.560 --> 03:08.760 So on the Internet, that's what they use when they interact with each other. 73 03:08.760 --> 03:11.240 They're using border gateway protocol. 74 03:11.240 --> 03:14.280 And in the world of BGP, each of these service providers is going to be 75 03:14.280 --> 03:16.280 assigned one or more 76 03:16.280 --> 03:19.880 numbers. And these are referred to as autonomous system numbers. 77 03:19.880 --> 03:22.200 Or for short, we just put AS. 78 03:22.200 --> 03:23.640 So let's say, for example, 79 03:23.640 --> 03:27.980 service provider A has been given the autonomous system number of one, one, one 80 03:27.980 --> 03:28.200 . 81 03:28.200 --> 03:32.080 And let's imagine that service provider B here has been given the autonomous WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 81 03:28.200 --> 03:32.080 And let's imagine that service provider B here has been given the autonomous 82 03:32.080 --> 03:33.000 system number of 83 03:33.000 --> 03:37.400 two, two, two, and service provider C. We're going to follow that same pattern 84 03:37.400 --> 03:40.760 and have it be assigned the autonomous system number of three, three, three. 85 03:40.760 --> 03:43.000 So in service provider A has a whole bunch of routers, 86 03:43.000 --> 03:46.440 and they're all running BGP to share and update routes with each other. 87 03:46.440 --> 03:50.440 Because in this example, all these routers are in the autonomous system, one, 88 03:50.440 --> 03:51.240 one, one, 89 03:51.240 --> 03:55.080 all these BGP neighborhoods are being formed between the routers here up at 90 03:55.080 --> 03:58.440 service provider A because they're all inside of this autonomous system, one, 91 03:58.440 --> 03:59.000 one, one. 92 03:59.000 --> 04:03.640 Those are referred to as internal BGP neighborhoods. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 92 03:59.000 --> 04:03.640 Those are referred to as internal BGP neighborhoods. 93 04:03.640 --> 04:06.040 So we'll call it I BGP for short. 94 04:06.040 --> 04:08.680 And the same thing would happen down here for all the routers at service 95 04:08.680 --> 04:09.320 provider B, 96 04:09.320 --> 04:13.160 where all the routers are participating as part of AS222. 97 04:13.160 --> 04:17.960 So that would be internal BGP neighborhoods between all these routers here at 98 04:17.960 --> 04:19.000 service provider B. 99 04:19.000 --> 04:22.120 And the same thing over here for service provider C with the autonomous system 100 04:22.120 --> 04:23.000 three, three, three, 101 04:23.000 --> 04:26.440 all these relationships here inside the service provider network, it'll be 102 04:26.440 --> 04:28.200 internal BGP neighborhoods 103 04:28.200 --> 04:29.960 because they're all within the same autonomous system. 104 04:29.960 --> 04:33.720 So if we took a user and we'll put that user's computer right there who's WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 104 04:29.960 --> 04:33.720 So if we took a user and we'll put that user's computer right there who's 105 04:33.720 --> 04:34.600 connected and getting 106 04:34.600 --> 04:38.800 internet access through service provider C, it's very possible this user, and 107 04:38.800 --> 04:39.560 we'll call this user 108 04:39.560 --> 04:43.780 user one. It's very possible they may be going to a resource that's reachable 109 04:43.780 --> 04:44.440 off of a network 110 04:44.440 --> 04:47.830 that's under the control of service provider A. So we'll go ahead and put the 111 04:47.830 --> 04:48.600 server up here. 112 04:48.600 --> 04:52.040 So if we want the internet to work and be able to route traffic everywhere, 113 04:52.040 --> 04:54.840 we're going to need some cooperation between the service providers because we 114 04:54.840 --> 04:55.400 also may have a 115 04:55.400 --> 04:58.760 server over here, for example, again, that this user may need access to. 116 04:58.760 --> 05:02.760 So to facilitate the sharing of routing information between service providers WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 116 04:58.760 --> 05:02.760 So to facilitate the sharing of routing information between service providers 117 05:02.760 --> 05:03.800 with BGP, 118 05:03.800 --> 05:07.800 we're going to go ahead and set up some connections, some neighborhoods between 119 05:07.800 --> 05:11.720 some routers in service provider A and some routers in service provider B and 120 05:11.720 --> 05:12.120 any other 121 05:12.120 --> 05:15.320 service providers that we need to directly share routing information with. 122 05:15.320 --> 05:19.800 So I'm going to use an orange color for the logical neighborhoods between a 123 05:19.800 --> 05:20.520 router here in 124 05:20.520 --> 05:24.520 service provider A and autonomous system 1111 and a router over here in service 125 05:24.520 --> 05:25.400 provider C 126 05:25.400 --> 05:28.920 in autonomous system three, three, three, and I'm also going to go ahead and do 127 05:28.920 --> 05:30.200 that here and here WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 127 05:28.920 --> 05:30.200 that here and here 128 05:30.200 --> 05:34.380 as well. And I'll do it here and here as well. And for fault tolerance, it's 129 05:34.380 --> 05:35.160 very likely we'd 130 05:35.160 --> 05:38.840 have more than just one single router from service provider A to service where 131 05:38.840 --> 05:39.400 B but for 132 05:39.400 --> 05:44.100 this diagram that'll work. Now these orange logical neighborhoods between these 133 05:44.100 --> 05:44.520 routers 134 05:44.520 --> 05:47.080 and different service providers, because they're setting up their neighborhoods 135 05:47.080 --> 05:47.880 between two routers 136 05:47.880 --> 05:51.880 in two different autonomous systems, for example, this router here, which I'll 137 05:51.880 --> 05:53.160 call router one, 138 05:53.160 --> 05:56.340 and then we call this one router two, and I'll call this one router three. So 139 05:56.340 --> 05:57.160 in the case of router 140 05:57.160 --> 06:00.590 one forming a neighborhood here with router three and a different autonomous WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 140 05:57.160 --> 06:00.590 one forming a neighborhood here with router three and a different autonomous 141 06:00.590 --> 06:00.920 system, 142 06:00.920 --> 06:05.400 because that relationship is between two BGP routers in two different 143 06:05.400 --> 06:06.440 autonomous systems, 144 06:06.440 --> 06:11.400 that relationship is referred to as an external BGP neighborhood. So all these 145 06:11.400 --> 06:12.360 connections here in 146 06:12.360 --> 06:16.470 orange are going to represent external BGP neighborhoods. Now there's a lot of 147 06:16.470 --> 06:17.640 rules of the road 148 06:17.640 --> 06:21.570 and options regarding tweaking border gateway protocol. And so our intent in 149 06:21.570 --> 06:22.120 this scale is 150 06:22.120 --> 06:26.030 just give you a high level overview of some of the basic concepts, and then put 151 06:26.030 --> 06:27.160 a game plan together 152 06:27.160 --> 06:31.230 and then walk through the configuration and verification between our tier zero WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 152 06:27.160 --> 06:31.230 and then walk through the configuration and verification between our tier zero 153 06:31.230 --> 06:31.720 gateway 154 06:31.720 --> 06:35.480 and an external BGP router. And in preparation for that, I'd also like to chat 155 06:35.480 --> 06:36.200 with you once again 156 06:36.200 --> 06:40.820 about administrative distance. So if you have a router that has learned the 157 06:40.820 --> 06:42.040 same exact route from 158 06:42.040 --> 06:45.550 two different sources, so let's pick this router right here. So if this router 159 06:45.550 --> 06:46.600 right here has learned 160 06:46.600 --> 06:52.740 about the network 66, 66, 66, zero with a 24-bit mask, and it learned about 161 06:52.740 --> 06:54.520 that via OSPF, 162 06:54.520 --> 06:57.960 and it learned about that same exact route from another source, but it learned 163 06:57.960 --> 06:58.200 it via 164 06:58.200 --> 07:02.670 internal BGP. And it also learned it from another source, but it was a external WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 164 06:58.200 --> 07:02.670 internal BGP. And it also learned it from another source, but it was a external 165 07:02.670 --> 07:03.480 BGP neighbor. 166 07:03.480 --> 07:07.230 That's an example of learning the same exact prefix fancy way for saying 167 07:07.230 --> 07:08.040 network reachability 168 07:08.040 --> 07:12.410 or a route, the same exact route three different ways. So in the event you have 169 07:12.410 --> 07:13.160 a router that's 170 07:13.160 --> 07:16.650 learning the same exact route from three different sources, who is it to 171 07:16.650 --> 07:18.360 believe? And the answer is, 172 07:18.360 --> 07:23.490 it's like golf and administrative distance. So each of these routing protocols 173 07:23.490 --> 07:24.200 has a default 174 07:24.200 --> 07:28.760 administrative distance. So SPF, that is 110 that we saw in the previous skill 175 07:28.760 --> 07:30.200 when we configured OSPF WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 175 07:28.760 --> 07:30.200 when we configured OSPF 176 07:30.200 --> 07:35.730 and adjacencies here between tier zero and the external routers. Internal BGP 177 07:35.730 --> 07:36.520 has a really, 178 07:36.520 --> 07:41.980 really terrible, meaning high default administrative distance, which is 200. 179 07:41.980 --> 07:44.120 And external BGP has a 180 07:44.120 --> 07:47.790 default administrative distance of 20. So what that means is that if we learn 181 07:47.790 --> 07:48.920 the same exact route 182 07:48.920 --> 07:52.600 from these three sources, the one that would make it into the routing table is 183 07:52.600 --> 07:53.800 the external BGP 184 07:53.800 --> 07:58.110 learned route with a better and lower like golf administrative distance. So let 185 07:58.110 --> 07:58.680 's clean this up 186 07:58.680 --> 08:03.100 a little bit and also talk about another use case for using BGP as a dynamic WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 186 07:58.680 --> 08:03.100 a little bit and also talk about another use case for using BGP as a dynamic 187 08:03.100 --> 08:04.520 routing protocol. 188 08:04.520 --> 08:08.460 Another use case is if we have a spine leaf architecture. So I'm going to go 189 08:08.460 --> 08:09.880 ahead and just put a couple 190 08:09.880 --> 08:13.410 of spine layer switches here. And then below that, I'm going to go ahead and 191 08:13.410 --> 08:14.440 put some top of racks 192 08:14.440 --> 08:18.780 which is here for this rack and a couple of top of racks, which is here for 193 08:18.780 --> 08:19.880 this rack and some top 194 08:19.880 --> 08:24.570 of racks, which is here for this rack. So this layer right here, which I'll go 195 08:24.570 --> 08:25.400 ahead and put a 196 08:25.400 --> 08:29.420 rectangle around this represents the leaf layer. And this layer right here 197 08:29.420 --> 08:30.760 represents the spine. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 197 08:29.420 --> 08:30.760 represents the spine. 198 08:30.760 --> 08:34.410 So our connections would look something like this. And this would be our spine 199 08:34.410 --> 08:35.320 layer. So a lot of 200 08:35.320 --> 08:38.840 times when we have a spine leaf architecture, we're going to be doing routing 201 08:38.840 --> 08:39.640 logical layer three 202 08:39.640 --> 08:43.830 routing between these racks, which also implies we have layer three routing set 203 08:43.830 --> 08:44.520 up between the 204 08:44.520 --> 08:48.380 leaf layer and the spine layer. So to share routing information there, we could 205 08:48.380 --> 08:49.640 also use OSPF 206 08:49.800 --> 08:54.100 if we wanted to, or we could use BGP to share that routing information. Either 207 08:54.100 --> 08:55.000 one would work 208 08:55.000 --> 08:58.490 as long as we're correctly sharing the reachability information so that the 209 08:58.490 --> 08:59.720 leaf and spine layers can 210 08:59.720 --> 09:02.810 make their forwarding decisions respectively. So let me clean that up a little WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 210 08:59.720 --> 09:02.810 make their forwarding decisions respectively. So let me clean that up a little 211 09:02.810 --> 09:03.720 bit. And let's talk 212 09:03.720 --> 09:07.830 about one last little aspect regarding BGP in general. And then we'll go to the 213 09:07.830 --> 09:08.840 next video where 214 09:08.840 --> 09:12.770 we'll put a game plan together. Let's imagine that we're running BGP and we 215 09:12.770 --> 09:14.280 have a router. And it has 216 09:14.280 --> 09:20.030 learned about the same exact network, let's go and put network 67 67 dot zero 217 09:20.030 --> 09:21.560 with a 24 bit mask. 218 09:21.560 --> 09:26.990 And it's learned that from two different E BGP neighbors. So there's our router 219 09:26.990 --> 09:27.400 . And over here, 220 09:27.400 --> 09:31.940 we'll have a BGP neighbor. That's an external neighbor. And over here, we have WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 220 09:27.400 --> 09:31.940 we'll have a BGP neighbor. That's an external neighbor. And over here, we have 221 09:31.940 --> 09:32.680 a BGP neighbor 222 09:32.680 --> 09:36.600 that's an external neighbor. And they're both advertising this network. So at 223 09:36.600 --> 09:37.000 that point, 224 09:37.000 --> 09:41.460 this router might say, well, they're both being advertised via external BGP. So 225 09:41.460 --> 09:42.120 the admission of 226 09:42.120 --> 09:46.990 distance is 20 for both of them. So now what do I do? So when it comes to the 227 09:46.990 --> 09:47.640 decision about, 228 09:47.640 --> 09:51.700 okay, which route which 67 67 is that a route? Am I going to put in a routing 229 09:51.700 --> 09:52.600 table and consider 230 09:52.600 --> 09:56.010 my best route? There are several decision points. But one of those is the 231 09:56.010 --> 09:57.560 length of the path and 232 09:57.560 --> 10:01.880 the world of BGP that boils down to the number of autonomous system numbers. So WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 232 09:57.560 --> 10:01.880 the world of BGP that boils down to the number of autonomous system numbers. So 233 10:01.880 --> 10:02.840 for example, 234 10:02.840 --> 10:06.520 when this route was advertised over here, perhaps as it was advertised, it said 235 10:06.520 --> 10:06.760 , Hey, 236 10:06.760 --> 10:11.730 regardless of this route, it went through as 67 and it went through as 95 and 237 10:11.730 --> 10:12.680 it went through as 238 10:12.680 --> 10:19.520 777. And over here, this route went through as 67 and as 213. And as a result, 239 10:19.520 --> 10:20.920 this one right here, 240 10:20.920 --> 10:25.230 because it went through less autonomous systems, effectively a shorter length 241 10:25.230 --> 10:26.200 of its path. It's 242 10:26.200 --> 10:29.920 this one that would be chosen to be used and put into the routing table as the 243 10:29.920 --> 10:30.680 route is going to WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 243 10:29.920 --> 10:30.680 route is going to 244 10:30.680 --> 10:34.210 use. So this router would still be aware of this additional route, but it 245 10:34.210 --> 10:35.320 simply wouldn't choose 246 10:35.320 --> 10:39.300 it as a preferred route because this one has a shorter autonomous system path 247 10:39.300 --> 10:39.960 associated 248 10:39.960 --> 10:43.380 with that route. All right, so now that we've taken a look at some of the use 249 10:43.380 --> 10:44.360 cases and some 250 10:44.360 --> 10:48.420 general characteristics regarding border gateway protocol in the next video, 251 10:48.420 --> 10:49.240 let's put a specific 252 10:49.240 --> 10:53.620 game plan together to use border gateway protocol between an external router 253 10:53.620 --> 10:55.080 here and our tier 254 10:55.080 --> 10:58.520 zero gateway. So I'll see you in the next video in just a minute.