Alright, so after all this trouble of setting up BGP both internally and externally, we're finally going to start Redistributing networks into BGP and see what happens when we send those networks to our BGP Neighbors. You've got some interesting issues to overcome when you're Redistributing from internal and external. So let's go over here to ISP 1 and let's Redistribute the networks that are in the ISP 1 Router into BGP. So if we do Show IP Interface Brief on this guy, we see that we have three networks, 50.10 11 and 12 as well as our Connected Networks going to our Neighbor Routers. So what we're going to do is go into Config Mode and we're going to do Router BGP and in this case I believe the AS is 127 yes, AS 127 on ISP 1. Router BGP 127 and we are going to use two different methods to get these networks into the BGP routing domain. Now we've talked about the Network Command and the fact that you have to be very specific with your network and your Network Mask in order to get those networks Redistributed. So we're going to do the Network Command for this 50.1 network. 188.8.131.52 slash 30. So we're going to do Network, I don't know what it is, I can never type that word right the first time. Network 184.108.40.206 Subnet Mask 255.255.255.252, oops I forgot the Mask Keyword, that is something else that's different with the Network Command. If I did Question Mark like I usually do, it would have been a lot more obvious there. So once we do that, we can specify a Route Map if we want to filter out specific Subnets within this network or if we want to Tag this network and we've discuss Route Maps elsewhere in the course. In this case, we're just going to Redistribute this network, network 10.1.1.0 with this Mask into BGP. So now if we go out here to ISP 1 and we do Show IP BGP we have to give BGP some time to, to synchronize and realize that we've added a network. So I'll pause the video and we'll come back once this network is being Redistributed into BGP. So now once we've waited for BGP to catch up with us, we see that we are Redistributing or more accurately, advertising the 220.127.116.11 slash 30 network into BGP routing domain. Now let's look at the output of the Show IP BGP Command. Obviously here's the network that's being advertised via BGP. Next hop is 0.0.0.0 meaning that it is a directly connected network on this router. Metric is zero obviously because it's a locally connected network. There's the Weight, 32,768 so as the Path is internal. Now again, we see all of this because we are getting this advertised to us via again a Local Network Connection. Over here on the very left hand side, you see that it is a valid route, meaning yes I can actually get to that network and this little carrot here, this greater than symbol means it is the best route to this network. Now we'll see this come into play later on once we get all of our BGP Routers online and advertising networks, you'll see multiple paths to the same network and obviously BGP like every routing protocol will pick one of the paths as the best path and that's what gets installed in the Routing Table. Now if we do Show IP Route obviously the directly connected route takes precedence over the BGP advertised route, as it is being advertised to itself. But because it is a directly connected network, the directly connected network takes precedence and that goes back to the Administrative Distance. Directly connected networks have an Administrative Distance of zero so you can never get better than directly connected. So now that this is being advertised by ISP 1, let's go look at our Access Routers. Obviously Core 1 is not participating in BGP, so Access 1 and Access 2 are the BGP Neighbors. Let's go over here and look at Access 1. Here's the Routing Table and the BGP Table for this guy. You'll see that this guy says it has a Router Information Base Failure. Now obviously it says it's the best route because it, again, it is a directly connected network, but it's saying that it sees as Internal BGP but it just doesn't really like that. So let's hit Up Arrow again and we've still got the same Status for this particular route in this Access 1 Router but that's not a big deal because again 10.50.1.10, that's not the right network. 18.104.22.168 is directly connected so let's go over to Access 2 and let's look at this guy. Now you'll notice that on Access 2 I've done Show IP BGP. It says yeah that's a valid route, but it's not the best route to the network. It says it's Internal but it's not the best so it's not going to install into the Routing Table. As an example, we do Show IP Route, we don't have any BGP Routes in the Routing Table. And the more astute among you may have noticed that the reason why is, look at the next hop here. The next hop is 22.214.171.124, well we don't have a route to get to the 126.96.36.199 host. Now this is one of the differences between Internal BGP and External BGP and some of the peculiarities of the Default Settings when you have External BGP Routes that are being sent to Internal BGP Neighbors. We'll figure out how to correct this or I'll show you how to correct this in the next video.
|Course:||Implementing Cisco IP Routing (642-902 ROUTE)|
|Duration:||10 hrs / 105 lessons|
|Captions:||Available on CD and Online University|
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