BGP Confederation Explained

Hello Rene,

Can you tell me if in GNS we have any kind of incompatibility with Confederations.

I did a lab on the GNS3 Cisco Router 7200, when I set up EBGP between R1 x R2 look at the messages.

Configurations?
R1:
image

R2:
image

AS error:
R2:


R1:

Thx

Hi Fabio,

Your config looks fine, it’s the same as mine:

R1#show run | section bgp
router bgp 1
 neighbor 192.168.12.2 remote-as 2
R2#show run | section bgp
router bgp 24
 bgp confederation identifier 2
 neighbor 192.168.12.1 remote-as 1

The error you get is about the BGP router ID:

BGP identifier wrong

Any chance you have the same router ID on R1 and R2?

Rene

Hi Rene,

I was making my own topology for BGP Confederation, I had divided one AS 2 into two sub AS, 100 and 200 and in each sub AS I had configured route -reflector, the router which is connected to the EBGP on both the Sub As is having an error for

 RIB-failure   RIB-NH Matches
88.1.1.0/24        88.1.1.2            Higher admin distance 

This is for both the Sub AS, can you please tell how I can fix it?

R7:

router ospf 2
 log-adjacency-changes
 network 7.7.7.0 0.0.0.255 area 0
 network 14.1.1.0 0.0.0.255 area 0
!
router bgp 200
 no synchronization
 bgp log-neighbor-changes
 bgp confederation identifier 2
 neighbor 6.6.6.6 remote-as 200
 neighbor 6.6.6.6 update-source Loopback0
 neighbor 6.6.6.6 next-hop-self
 neighbor 88.1.1.2 remote-as 3
 no auto-summary

R8:

R8#sh run | s bgp
router bgp 3
 no synchronization
 bgp log-neighbor-changes
 network 8.8.8.0 mask 255.255.255.0
 network 88.1.1.0 mask 255.255.255.0
 neighbor 88.1.1.1 remote-as 2
 no auto-summary
R8#

Hello navarj

This failure is due to the fact that there seems to be routing information about this route that is coming from another source that has a lower administrative distance (BGP has the higher AD so it fails or loses, and the route is not added). Can you check to see the source of that higher AD and see where it is coming from? If you find that out, then you can adjust ADs to result in the BGP routes that you want installed.

I hope this has been helpful!

Laz

Hi Laz,

88.1.1.2 is the interface of R8 from where I had configured BGP on this router which has interface add 88.1.1.1, I need to increase AD on R8 as it is on different AS 3 and R7 is on A2.
Can you please upload any videos on it so which can help why it occur where we use iBGP internally and what is the best solution to fix this issue.

Hello Navaraj

Forgive me, but I’m still trying to understand the nature of the problem. Why are you changing the AD on R8, and if so, I don’t see it in your configuration. And if you’re getting an issue with AD, this means that the router is learning of the route from a different source, which we don’t see in what you provided. Can you clarify further so that we can aid in troubleshooting?

Thanks in advance!

Laz

Hi Laz,

R1 is in AS 1, R2, R3, R4, R5, R6, R7 are in AS 2, R3 is in AS 3.
All the neighborship between AS are done via loopback address and in AS2 I am using OSPF to advertise the connectivity, in iBGP I had configured two RR servers that is R3 and R6, I am able to ping from AS 3 to AS 1, but internally in AS 2 i am not able to ping R8 or R1 and the router R2 and R7 are showing

RIB-failure RIB-NH Matches
88.1.1.0/24 88.1.1.2 Higher admin distance

What is solution to fix it? Which node I have configure and why I am getting this problem.

Hello Navaraj

The RIB failure is not necessarily a problem. It seems here that R7 sees that it has a directly connected route of 88.1.1.0/24 in its routing table, which automatically outranks the AD of the route learned via BGP, which is as it should be.

My question is, why does R7 receive routing information to a network that is directly connected? Is 88.1.1.0/24 being advertised via OSPF as well? Can you clarify this information so we can further troubleshoot?

Thanks!

Laz

Hi Laz,

Yes, 88.1.1.0/24 is directly connected between R7 and R8, EBGP is configured via R7 and R8 on the interface which has ip add 88.1.1.0/24. I had advertised 88.1.1.0/24 on R8 via BGP, there is no OSPF advertisement of this network.

Hello Navaraj

The RIB-failure statement you are getting states that the router is learning of the 88.1.1.0/24 network from BGP. This however is a directly connected network, and should be in your routing table as such. The conflict comes from the fact that the AD of the directly connected route outranks the AD of the route being learned via BGP. However, my question is WHY is BGP advertising this route to a router that is directly connected to it? Can you investigate in this direction?

I hope this has been helpful!

Laz

Hi Laz,

I had advertised this network on R8 under BGP, that’s why it is advertised.

Hello Navaraj

Then it is natural that you will have such a message from BGP. This is not necessarily incorrect, and based on the design, is to be expected. The problem you are facing is independent of the specific BGP message that you are sharing. You will have to look elsewhere for the specific problem.

Our goal here is to help you pinpoint the problem by giving some guidelines, or information concerning the next steps to take. I hop this helps you in your troubleshooting procedures.

Laz