Thanks for information,

As 65510 R1----------R2 AS 65520

---------------------------------------------Both R1 and R2 comes under Public AS of 20

What i want to know is whether the TCP connection will establish without giving the command as

R1 # BGP Conferderation peer 65520

and in

R2 # BGP Conferderation peers 65510

Regards,

vinoth

Hi, vinoth

Without the bgp confederation peer command, both routers will see each other as a true EBGP peer. R1 will send an open message with AS=20 to R2 and expect to recevie an open message from R2 with AS=65520.

R2 do the same thing.(send an open message with AS=20 and expect to receive an open message with AS=65510). And the result is a wrong-AS issue. Theorectically, the BGP session cannot be established.

And why did your routers can establsh the session successfully? I don't know. Wait the expert to answer you.(Harold, where are you?) Before that, it's a good idea to issue the debug ip bgp command on your routers and see what messages are brought to you.

HTH

SSLIN

SSLIN,

You are correct the session should not come up given the above scenario.

Vinoth,

Can you provide the full configurations from both R1 and R2 that led to that mysterious behavior.

Regards,

20.0.0.1/8 .2

R2 ----------------- R3

As|65510 As 65520

-----|------------------------------

| Public As 20

|

|10.0.0.1/8

R1

Public As 10

R1#Router bgp 10

#neighbour 10.0.0.2 remote-as 65510

#network 10.0.0.0

R2#router bgp 65510

#neighbour 20.0.0.2 remote-as 65520

#neighbour 10.0.0.1 remote-as 10

#bgp conferderation identifier 10

R3#router bgp 65520

#neighbour 20.0.0.1 remote-as 65510

This what i have done in my home lab and i found that the adjacency is formed between the routers

can u suggest me were is the route cause for this issue

Note : R2 is running on version 12.2 (5)

R3 is running on version 12.2 (8)

Thanks in advance,

vinoth

Hi, Vinoth

I try your config and the result is the same.

R2's debugging message

received from neighbor 20.0.0.2 2/2 (peer in wrong AS) 2 bytes 0014

R3's debugging message

BGP: 20.0.0.1 bad OPEN, remote AS is 20, expected 65510

show ip bgp summary on R2

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

20.0.0.2 4 65520 8 8 0 0 0 never Active

show ip bgp summary on R3

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

20.0.0.1 4 65510 8 8 0 0 0 never Active

Would you please post your output of "debug ip bgp" and "show ip bgp summary"?

SSLIN

This is not normal. I tried with 12.2(10) and the session didn't come up.

You are probably running in to some older bug. I would suggest you try with more recent code, in which case you should see that the session won't form.

Hope this helps,