Implementing Cisco IP Routing (642-902 ROUTE) Tutorials
BGP / Lab - iBGP Configuration
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Subtitles of the Movie (Implementing Cisco IP Routing (642-902 ROUTE) / BGP / Lab - iBGP Configuration)
So we're continuing on with our BGP Configuration. Now we're going to move onto configuring IBGP. We're going to configure IBGP between Access 1 and Access 2. Now you might be looking at the Network Diagram and say well Access 1 and Access 2 aren't directly connected, they're on two different IP Subnets, how can they be neighbors? Your neighbors have to be directly connected. Right. Well when you're talking about EIGRP and OSPF and other IGPs, yes they do have to be directly connected. However, we're not talking about those, we're running BGP and BGP as you'll recall just uses TCP for it's transport assuming that you can Ping from Access 1 to Access 2, you can establish a BGP Neighbor Relationship between these two Routers. But first let's verify that we can actually Ping between them and I know we can because I set up the lab. We'll go on Access 1 and we'll Ping 10.20.2.2 from Access 1. Ping 10.20.2.2 and there you go, you can Ping through the Core 1 Router over to Access 2. So now let's set up IBGP between these two Routers. We'll open up the Console on this guy first, we'll configure this end and then we'll go back over to Access 1. So we'll go onto this guy, go into Enable, Config T, Router BGP 12, since we're are on Autonomous System 12 on this guy. Now we're going to do Neighbor, Neighbor and in this case the Neighbor will be 10.20.1.2. Neighbor 10.20.1.2 and even though we're in the same Autonomous System, if we just hit Enter here, it's going to say Incomplete Command. We have to specify the Remote AS saying the other guy is an Autonomous System 12 and at that point the BGP process says, well his Autonomous System is the same as mine so I'm running IBGP and we'll change the way the rules work a little bit. So we'll do Remote AS 12. Now that we've got Access 2 configured, we'll do Show IP BGP Summary just to make sure that it is looking for the other guy. And he's out there looking. Now again, Access 1 is already running BGP however since you have to manually configure the neighbor, it's looking at the BGP Requests coming in from Access 2 and saying well I don't know who you are. Your, your not a neighbor of mine, I, I've never heard of you before and so I'm not going to establish a Neighbor Relationship with you and again going back to the overview video, that's by design and it's by a good thing, otherwise, you know, someone with a misconfigured BGP Router at a customer site somewhere, someone who really, really wants to learn about BGP could just Peer with an ISP and you know, well there goes the Internet. So let's go back over to Access 1 and set up Access 2 as a neighbor. So go over to Access 1, Config T, Router BGP 12, we'll do Neighbor 10.20.2.2, Remote AS 12. And so now as we've mentioned, we have to wait for BGP to come up. Again this may take a few seconds, so I'll just pause the video until the neighbor adjacency establishes and then we'll carry on. Alright, so you see that it finally established. If we go in here and we redo Show IP BGP Summary we see that it's been up for sixteen seconds now and we've received no prefixes and we're communicating with this guy. Shows that he's on Autonomous System 12. However, we're still not trading routes via BGP. We'll do Show IP Route, obviously we only routes we're learning about are directly connected or via OSPF and in fact if we just issue the Command Show IP BGP, we see there's nothing in the BGP table at all. We got neighbors, we're communicating. In Access 1 we're actually communicating with multiple Autonomous Systems but we're still not sending routes around the network. We'll get to it never fear. In fact, let's go ahead now and Redistribute our Internal Routes into our IBGP Session. Now obviously the first thing we want to do is, we want to set up a Route Map because we don't want for the time being our Internal Routes to leak out to our ISP Routers. And if we just flat out set up Redistribution then once it gets into BGP it'll end up on all of the Routers that BGP knows about. But let's say that we just forgot about that, we're, we're going to go in and say, well we're just going to Redistribute our networks into BGP. Let's just do that and see what happens. So we'll go here to Access 1, that's where we'll do Redistribution at, we'll actually do it on Access 2 as well. So we'll go into Config Mode, Config T, do Router BGP 12 and we're going to use the Network Command. Now the Network Command works a little differently in BGP than it does with other Internal Gateway Protocols. See before, I, I could say well I want to advertise everything that starts with 192.168 so I could put in 192.168.0.0 0.0.255.255. That won't work in BGP. First off BGP doesn't use the, the Bit Mask, it actually uses the Network Mask. So even if we were to substitute that correctly, 255.255.0.0 that will not actually advertise any networks into BGP. The reason why is that if you're going to specify a network, you've got Auto Summary turned off, first off, but if you're going to specify a network, you have to match the Network Mask exactly. So I would have to use the Network Command 192.168.10.0 255.255.255.0 and do each one of these networks individually. So now that we've gone over the basics of how the Network Command works, we'll save that all for the next video.
Tutorial Information
| Course: | Implementing Cisco IP Routing (642-902 ROUTE) |
| Author: | Greg Dickinson |
| SKU: | 34291 |
| ISBN: | 978-1-61866-028-2 |
| Release Date: | 2011-12-28 |
| Duration: | 10 hrs / 105 lessons |
| Work Files: |
Yes |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |
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