[c-nsp] 7604 12.2(33)SRC6

[Shimol Shah]

This has been seen in the past when peering box had peer to SRC box 
shutdown, but was still accepting the TCP connection. Normally the tcp 
connections should not be accepted unless some bgp neighbor is active.

For the scenario where this was seen it was seen that peer router 
accepts this and brings the bgp session down and that is the reason why 
Cisco router tries to establish again and the messages being logged.

The most appropriate workaround is to make the transport session as 
passive. Otherwise shutting down the neighbor in question or 
un-configure bgp log-neighbor changes should also work.

We opened a bug for it, but after above triage it was closed as issue 
was not at Cisco side and workarounds could be put in place on Cisco 
side to prevent same.


+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

CSCte95094    BGP "Unknown path error" message is output repeatedly

Symptom:

"Unknown path error" message repeatedly logged after "neighbor shutdown"
  issued on a peering router.


Conditions:

An IPv6 eBGP peer is formed between a cisco router and a 3rd-party router.
Neighbor is shutdown manually on the 3rd-party router.


Workaround:

"neighbor x.x.x.x connection-mode passive" may be a workaround.


+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++


If above does not apply or as an FYI below is good to be aware of,

=======================================================================

CSCsy10339    bgp:messages:topology base removed from session Unknown 
path error


Symptom:
%BGP_SESSION-5-ADJCHANGE reports Unknown path error on receiving a
NOTIFICATION


Conditions:
OPEN collision or a peer repeatedly rejecting an OPEN with an invalid AS.

Workaround:
clear ip bgp * on the receiving peer may help


=====================================================================


HTH

Shimol


On 7/26/10 9:08 PM, g00d3vil wrote:
> Hello,
>
> I have a strange problem with a BGP session, i get the error message:
>
> ul 27 02:48:30: %BGP_SESSION-5-ADJCHANGE: neighbor 81.22.150.214 IPv4
> Unicast topology base removed from session  Unknown path error
> Jul 27 02:48:43: %BGP_SESSION-5-ADJCHANGE: neighbor 81.22.150.214 IPv4
> Unicast topology base removed from session  Unknown path error
> Jul 27 02:48:52: %BGP_SESSION-5-ADJCHANGE: neighbor 81.22.150.214 IPv4
> Unicast topology base removed from session  Unknown path error
>
>
> This is after the upgrade from SRC1 to 12.2(33)SRC6 , then SRE1
>
> Din anyone of you encountered this problem? What is the workaround? Should I
> rollback to my previous IOS or other version.
>
> Thank you,
>
> paulm
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