Sunday, April 16, 2017

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Troubleshooting MultiProtocol BGP(MP-BGP) Issues

                            Now the we have considered some of the Troubleshooting issues surrounding BGP, let’s now consider Multi-Protocol BGP, Multiprotocol BGP allows us to support BGP Routing for IPv6
                And there is similar consideration to Troubleshooting Multiprotocol BGP as there are Traditional BGP however, i want to use this topic to point out a couple of differences and some extra things to keep in mind for one thing if Routing IPv6, we need to make sure that the Router is enabled for IPv6 unicast-routing, let’s do a
Ø  R1(config)#ipv6 unicast-routing
                               Now we are enabled for IPv6 and there is something else that’s not is obvious going on here, we got a couple of ways setting this up, we could do IPv6 Routing over an IPv4 session or we could do IPv6 Routing over an IPv6 session and i want you to show you the Configuration for both and this topology, i have got an IPv4 session setup between Router R1 and R2, let’s take a look at the Configuration.
Ø  R1#show run | section router
                          And you gonna see this looks lot like, the EIGRP Named Configuration or the Address-Families configuration for OSPF, that’s what we have got here, we got an Address-family for IPv4 and we got another Address-family for IPv6. Notice we go into Router BGP Configuration Mode similar to have we do with Traditional BGP or the way we normally talk about Traditional BGP as being BGP Version 4.
                         Please understand this is also technically BGP Version 4, it’s just that we have some extra extensions added when we have Multiprotocol BGP but technically still Version 4 and i am specifying my neighbor and Remote Autonomous System number and i am using IPv4 address to specify the neighbor when it comes to Troubleshooting though, here is the one of first thing i want you to think about for your IPv6 Address-Family if you are doing this over an IPv4 session you need to specify a Route-Map for that neighbor
                         That’s going to specify what next Hop IPv6 address it should use and this is Next Hop information, note that Router R1 is using this is next Hop-Router information, that R1 is telling to Router R2, we are telling R2 how to get back to us, we are specifying ourselves, we specifying our IPv6 address, let’s take a look at this Route-Map
Ø  R1#show route-map
                                                     And you can see that, we are setting our IPv6 next-hop to 2000:2::1 and if you take a look at our topology that’s us, we are telling Router R2 use this IPv6 Address to get back to us if we don’t do this then any Routes that we advertised to Router R2 they are not gonna be injected into Router R2’s IP Routing Table because Router R2 would not know how to get back to us, it would not know how to get to the next-hop so, if we doing this over an IPv4 session, we need to specify that Next-Hop.
                               And those are couple of things to keep in mind if we doing IPv6 Routing over an IPv4 BGP session and i want you to show you for contrast what a configuration looks like if we doing IPv6 Routing over an IPv6 BGP session, i am going to update the configuration on this topology right now, and we check that out.
                                 In this topology, i have got an IPv6 BGP session setup between Router’s R1 and R2 and we are doing IPv6 Routing over that IPv6 session and i wanted you to contrast this configuration vs the configuration where we doing IPv6 Routing over IPv4 BGP session, let’s do a
Ø  R1#show run | include router
                          And here you see that configuration is bit simpler, it still using this address’s family approach but i am specifying as my neighbor an IPv6 address and notice that under the IPv6 address-family, there is no need to have a Route-Map Configured as we did a few movements ago when we had a IPv4 BGP session.

                          Now this does not mean we cannot do IPv4 Routing as well over BGP it’s just that we would have to setup that separately and that would requires to have here adjacency that might not scale very well for very large network, we get lots of neighbors each of which running IPv4 and IPv6 but in, some cases this is more efficient approach maybe you only want to do IPv6 Routing and If you do this is a fairly simple way to set it up and we do not have to worry about creating a Route-Map.


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