[lumenok]

CSCva92216
Help  | Feedback Feedback
BGP session is reset when unrecognized capability received in OPEN message
CSCva92216
Description
Symptom:
BGP session will not come up with peer if an unrecognized or unsupported capability is received from the peer in the BGP OPEN. Message similar to the following might be observed:

Aug  4 16:20:22.627: %BGP-3-NOTIFICATION: sent to neighbor 10.100.100.100 active 2/0 (open: unspecific subcode) 0 bytes
Aug  4 16:20:22.627: %BGP-4-MSGDUMP: unsupported or mal-formatted message received from 10.100.100.100:


Expected behavior is that the local device should ignore the unrecognized/unsupported capability and bring the session up with the known capabilities, but that does not occur.

Conditions:
Local device is an IOS or IOS-XE device running a release that has the changes introduced in CSCuz20869.

Remote BGP peer sends a BGP OPEN which advertises a capability that is not recognized or not supported by the local device.

Workaround:
Identify the unsupported capability that is being advertised, and reconfigure the remote peer to suppress advertisement of this capability. The exact method to do so will vary based on the remote peer's platform, software version, etc;

The unsupported capability can be identified by enabling "debug bgp ipv4 unicast in" on the local peer. For example the following debug messages tell us that the peer is sending as BGP capability 5 which is not supported by the local peer:

*Sep 11 18:31:14.867: BGP: 10.128.129.134 active OPEN has CAPABILITY code: 5, length 6
*Sep 11 18:31:14.867: BGP: 10.128.129.134 active unrecognized capability code: 5
*Sep 11 18:31:14.867: BGP: 10.128.129.134 active malformed/un-supported OPEN capability
*Sep 11 18:31:14.867: BGP: 10.128.129.134 active went from OpenSent to Closing
*Sep 11 18:31:14.867: %BGP-3-NOTIFICATION: sent to neighbor 10.128.129.134 active 2/0 (open: unspecific subcode) 0 bytes

Further Problem Description:
This defect is unintended collateral caused by the fix of CSCuz20869. If a given release does not have the prior fix, then it is not impacted by this problem.

Никто не словил еще такой же сюрприз на cisco по bgp?

Описание на cisco.com

 

[Pinkbyte]

Эта как раз причина, почему я в своё время перекатился с 16.3 на 16.6 - после апгрейда на 16.3 тупо не подымалась сессия с одним из аплинков