BGP Confederation Config help!

[xaeravoqxaeravoq]

I can get BGP working just fine when I am not using confederations. After attmpting to config a confederation, R4 keeps getting messages that R2 is in the wrong AS. Here are the configs for R2 and R4. I edited the configs to only show each routers config to each other. The error message is "%BGP-3-NOTIFICATION: received from neighbor 2.2.2.2 2/2 (peer in wrong AS) 2 bytes 0001". I am using GNS3 and am not sure if I am doing something wrong if GNS3 is the problem. Any help would be greatly appreciated. Thank you.

R2

router bgp 1

neighbor 4.4.4.4 remote-as 64512

neighbor 4.4.4.4 ebgp-multihop 3

neighbor 4.4.4.4 update-source Loopback0

R4

router bgp 64512
bgp confederation identifier 1

neighbor 2.2.2.2 remote-as 1
neighbor 2.2.2.2 ebgp-multihop 2

neighbor 2.2.2.2 update-source Loopback0

[Reza Sharifi]

Confederation is used for IBGP not EBGP. If you put r2 and r4 in the AS, the message should go away

HTH

Reza

[esomarriba]

Hi Mike,

Do you have a network diagram you can share with us?

To configure a BGP confederation, you must specify a confederation identifier. To the outside world, the group of autonomous systems will look like a single autonomous system with the confederation identifier as the autonomous system number. To configure a BGP confederation identifier, perform the following tasks in router configuration mode:

By looking at your configuration you are missing:

bgp confederation identifier autonomous-system &

bgp confederation peers autonomous-system [autonomous-system ...]

HTH,

Elyinn.-

NOTE: What are you trying to accomplish? What's your scenario?

[courageux]

Hello Mike,

This is your config .....

R2

router bgp 1

neighbor 4.4.4.4 remote-as 64512

neighbor 4.4.4.4 ebgp-multihop 3

neighbor 4.4.4.4 update-source Loopback0

R4

router bgp 64512
bgp confederation identifier 1

neighbor 2.2.2.2 remote-as 1
neighbor 2.2.2.2 ebgp-multihop 2

neighbor 2.2.2.2 update-source Loopback0

If you just want to bring the BGP to form a neighbor relationship, in your config, there is only one thing that is missing. You just need to add bgp confederation identifier 1 command to R2. This will bring up the neighbour right away. Now, why do you need that? Its a requirement to have confederation configured. In other words, R4 sends the packet with the confed-id but R2 doesn't expect to see that. Well, thats why it doesn't understand that. You tell R2 that the packet will  come with a confed-id and the peering will come up.

HTH

[xaeravoqxaeravoq]

Hi, I have attached a picture of my network topology. I am trying to have R4 in a confederation with R9 and R10. R2 is NOT in the confederation. I can get R4, R9 and R10 talking together in a confederation but then R4 will not peer with R2 or R3 (i have the same problem with R3).  I go into the BGP process for the Sub-AS (64512) then type bgp confederation identifier 1 to identidy the "global" AS number.

[courageux]

Mike,

I am assuming that R4 <> R2 and R4 <> R3 are EBGP peers. On R4, you have to have the AS# which you use on R2's neighbor statement.

So, this is how it will look R4

R4

Router bgp xxxxx

bgp confederation identifier xxxxx

neighbor (R2) remote-as public-as (AS # you have used on R2)

neighbor (R3) remote-as public-as (AS # you have used on R2)

neighbor (R9) remote-as private-as

neighbor (R10) remote-as private-as

R9

Router bgp private-as

bgp confederation identifier xxxxx

neighbor (R2) remote-as XXXXX

neighbor (R10) remote-as private-as (it could be the same private AS or you could run a different one R10)

R10

Router bgp private-as

bgp confederation identifier xxxxx

neighbor (R2) remote-as XXXXX

neighbor (R9) remote-as private-as (it could be the same private AS or you could run a different one R10)

Note, if you use two different private-as, you will have confederation peer command specifying the opposite ends for each sub-as.

Let us know if this works for you.

[courageux]

Sorry, xxxxx or XXXXX are the same numbers.

[xaeravoqxaeravoq]

thank you for the response. i just got back from vacation so i am now taking a look. i am still very, very confused. on R4 if i just have:

router bgp 64512

no synchronization

bgp log-neighbor-changes

bgp confederation identifier 1

neighbor 2.2.2.2 remote-as 1

neighbor 2.2.2.2 update-source Loopback0

no auto-summary

R2 detects the neighbor but the status of show bgp sum shows:

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

4.4.4.4         4    64512      14     14             0         0          0   never        Active

if i go to R4 and add the neighbor 2.2.2.2 ebgp-multihop 2 command i then start receiving that message saying that R4 is in the wrong AS...

Am i correct I thinking that only R4, R9, and R10 will need the bgp confederation identifier commands since they are going to be the only routers in a confederation in the AS? All other routers are not in any sort of confederation but they are still in my AS.

[cadet alain]

Hi,

You must partition your AS in multiple subASes. I never saw an iBGP relationship between a confederation member and a non confederation member. R2 must either be in another subAS or it must be in another AS.

Regards.

Alain.

[xaeravoqxaeravoq]

well that explains why i was so confused. thank you so much. this has been driving me crazy!