KB Knowledge Base
BGP for IPv6 - iBGP Full Mesh

Article By algert01


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Introduction to BGP IPv6

In this tutorial I will be configuring the BGP for IPv6 router iBGP Full Mesh.  I will start off with the baseline show command, “show BGP IPv6, unicast summary” to display general information about IPv6 BGP neighbors. Then I am going to enable a debug command “debug BGP IPv6 unicast” to see how things unfold as I configure the BGP for IPv6 router iBGP Full Mesh. Finish with the same baseline command, “show BGP IPv6 unicast summary” to see what changed.



Let’s look at the network topology.



BGP IPv6 network topology

I will be configuring the BGP for IPv6 iBGP Peer full mesh between Router 2, 3, 4, 5 and Router 6. Previously I have configured OSPFv3 to advertise all interface addresses and loopback addresses too and also enabled BGP for IP6 on all routers.
Like other EGPs, BGP must completely understand the relationships it has with its neighbors. Therefore, this task is required.

BGP supports two kinds of neighbors: internal and external. Internal neighbors are in the same autonomous system; external neighbors are in different autonomous systems. Normally, external neighbors are adjacent to each other and share a subnet, while internal neighbors may be anywhere in the same autonomous system.

I will enter my show command “show bgp ipv6 unicast summary” on Router 2 to see BGP peers on this Router.

BGP IPv6 network

A full mesh is just that. Every iBGP speaker talks BGP to every other iBGP speaker. For example, R2 has an adjacency to three, five, six, and four. Also, three has an adjacency with two, four, five, and six. And as you can see, this goes on and on until you get the full mesh you need throughout your AS.

From the output of show command I see that there is only a peer which corresponds to Router 1, that is an external peer.

As I can see from the output of show command, there is only one neighbor in Router 2 which I have configured before. It is Router 1 and it is an external neighbor with AS 1.

I am going to configure BGP for IPv6 Peers on Router 2. This time I am using loopback interface to form peers.

I am entering command “neighbor 2001:3:3:3::3 remote-as 23456” on BGP configuration mode followed by command “neighbor 2001:3:3:3::3 update-source loopback 0” to specify the source which is used to form BGP neighbors and activating by the command “neighbor 2001:3:3:3::3 activate”.


At the same time I will enable debugging utilizing command: “debug bgp ipv6 unicast

There is still no change since I have configured nothing at Router 3 side. I am going to repeat this steps in Router 2 configuration to create peers with Router 4, Router 5 and Router 6 utilizing commands:

neighbor 2001:4:4:4::4 remote-as 23456
neighbor 2001:5:5:5::5 remote-as 23456
neighbor 2001:6:6:6::6 remote-as 23456


neighbor 2001:4:4:4::4 update-source loopback 0
neighbor 2001:5:5:5::5 update-source loopback 0
neighbor 2001:6:6:6::6 update-source loopback 0

and the last to activate neighbors

neighbor 2001:4:4:4::4 activate
neighbor 2001:5:5:5::5 activate
neighbor 2001:6:6:6::6 activate

Now I am going to configure the same commands on Router 3, crating peers for Router 2, Router 4, Router 5 and Router 6.

neighbor 2001:2:2:2::2 remote-as 23456
neighbor 2001:4:4:4::4 remote-as 23456
neighbor 2001:5:5:5::5 remote-as 23456
neighbor 2001:6:6:6::6 remote-as 23456

neighbor 2001:2:2:2::2  update-source loopback 0
neighbor 2001:4:4:4::4 update-source loopback 0
neighbor 2001:5:5:5::5 update-source loopback 0
neighbor 2001:6:6:6::6 update-source loopback 0

and the last to activate neighbors
neighbor 2001:2:2:2::2  activate
neighbor 2001:4:4:4::4 activate
neighbor 2001:5:5:5::5 activate
neighbor 2001:6:6:6::6 activate

As I enter the commands in Router 3, from the debug output on Router 2, I see Router 2 and Router 3 forming a BGP adjacency.

From the debug output in Router 2 I see routers sending and receiving messages and then establishing an adjacency.

BGP Network

Now I am going to configure peers on Router 4, Router 5 and Router 6 using the same commands.

As I configured peers on Router 4, Router 5 and Router 6 I could see from the debug command on Router 2 adjacencies being formed.

Now I am utilizing again my show command “show bgp ipv6 unicast summary” on Router 2 to see what is changed.

BGP IPv6 Network

From the output of show command I see that there are 4 neighbor on Router 2.

I am entering show command on rest of the routers.

From the output of show command I can see that all routers have peers all the other routers on this AS. I have created a full mesh iBGP.

In tutorial, I configured the BGP for IPv6 router iBGP Full Mesh.  I started off with the baseline show command, “show bgp ipv6 unicast summary” to display general information about IPv6 BGP neighbors. Then I enabled a debug command “debug bgp ipv6 unicast” to see how things unfold as I configured the BGP for IPv6 router iBGP Full Mesh. Finished with the same baseline command, “show bgp ipv6 unicast summary” to see what changed.

Summary steps:


R2
show bgp ipv6 unicast summary
debug bgp ipv6 unicast
!
conf t
router bgp 23456
neighbor 2001:3:3:3::3 remote-as 23456
neighbor 2001:4:4:4::4 remote-as 23456
neighbor 2001:5:5:5::5 remote-as 23456
neighbor 2001:6:6:6::6 remote-as 23456

neighbor 2001:3:3:3::3 update-source loopback 0
neighbor 2001:4:4:4::4 update-source loopback 0
neighbor 2001:5:5:5::5 update-source loopback 0
neighbor 2001:6:6:6::6 update-source loopback 0


address-family ipv6
neighbor 2001:3:3:3::3 activate
neighbor 2001:4:4:4::4 activate
neighbor 2001:5:5:5::5 activate
neighbor 2001:6:6:6::6 activate
!
R3
!
conf t
router bgp 23456
neighbor 2001:2:2:2::2 remote-as 23456
neighbor 2001:4:4:4::4 remote-as 23456
neighbor 2001:5:5:5::5 remote-as 23456
neighbor 2001:6:6:6::6 remote-as 23456
neighbor 2001:2:2:2::2 update-source loopback 0
neighbor 2001:4:4:4::4 update-source loopback 0
neighbor 2001:5:5:5::5 update-source loopback 0
neighbor 2001:6:6:6::6 update-source loopback 0
address-family ipv6
neighbor 2001:2:2:2::2 activate
neighbor 2001:4:4:4::4 activate
neighbor 2001:5:5:5::5 activate
neighbor 2001:6:6:6::6 activate
!
R4
!
conf t
router bgp 23456
neighbor 2001:2:2:2::2 remote-as 23456
neighbor 2001:3:3:3::3 remote-as 23456
neighbor 2001:5:5:5::5 remote-as 23456
neighbor 2001:6:6:6::6 remote-as 23456
neighbor 2001:2:2:2::2 update-source loopback 0
neighbor 2001:3:3:3::3 update-source loopback 0
neighbor 2001:5:5:5::5 update-source loopback 0
neighbor 2001:6:6:6::6 update-source loopback 0
address-family ipv6
neighbor 2001:2:2:2::2 activate
neighbor 2001:3:3:3::3 activate
neighbor 2001:5:5:5::5 activate
neighbor 2001:6:6:6::6 activate
!
R5
!
conf t
router bgp 23456
neighbor 2001:2:2:2::2 remote-as 23456
neighbor 2001:3:3:3::3 remote-as 23456
neighbor 2001:4:4:4::4 remote-as 23456
neighbor 2001:6:6:6::6 remote-as 23456

neighbor 2001:2:2:2::2 update-source loopback 0
neighbor 2001:3:3:3::3 update-source loopback 0
neighbor 2001:4:4:4::4 update-source loopback 0
neighbor 2001:6:6:6::6 update-source loopback 0

address-family ipv6
neighbor 2001:2:2:2::2 activate
neighbor 2001:3:3:3::3 activate
neighbor 2001:4:4:4::4 activate
neighbor 2001:6:6:6::6 activate
!
R6
!
conf t
router bgp 23456
neighbor 2001:2:2:2::2 remote-as 23456
neighbor 2001:3:3:3::3 remote-as 23456
neighbor 2001:4:4:4::4 remote-as 23456
neighbor 2001:5:5:5::5 remote-as 23456

neighbor 2001:2:2:2::2 update-source loopback 0
neighbor 2001:3:3:3::3 update-source loopback 0
neighbor 2001:4:4:4::4 update-source loopback 0
neighbor 2001:5:5:5::5 update-source loopback 0

address-family ipv6
neighbor 2001:2:2:2::2 activate
neighbor 2001:3:3:3::3 activate
neighbor 2001:4:4:4::4 activate
neighbor 2001:5:5:5::5 activate
!

R2
show bgp ipv6 unicast summary
R3
show bgp ipv6 unicast summary
R4
show bgp ipv6 unicast summary
R5
show bgp ipv6 unicast summary
R6
show bgp ipv6 unicast summary




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