Hello, i have little weird problem with route selection in bird. A have four routers in my AS, routers called R1 and R2 is running guagga, routers called R3 and R4 is running bird 1.2.5. I have configured full mesh between all of them.
IP 81.xxx.yyy.189 and 81.xxx.yyy.190 is ebgp peers. Both, R3 and R4 running bird have established peer with both ebgp routers. IP 109.xxx.yyy.11 and 109.xxx.yyy.12 is IP on R3 respectively R4 (ibgp interconnection) After receive this withdraw from ebgp peer 81.xxx.yyy.189 by R3 for example: 14:19:23.930683 81.xxx.yyy.189 81.x.yyy.185 BGP UPDATE Message Withdrawn prefix: 187.120.96.0 (187.120.96.0) bird do this: - switch route between ebgp and ibgp peer very fast - 288 times (in one second) in this case: 14:19:25 <TRACE> kernel1 < replaced 187.120.96.0/23 via 81.xxx.yyy.190 on bond0.402 14:19:25 <TRACE> kernel1 < replaced 187.120.96.0/23 via 109.xxx.yyy.12 on bond0.403 14:19:25 <TRACE> kernel1 < replaced 187.120.96.0/23 via 81.xxx.yyy.190 on bond0.402 which generates a lot of withdraw/updates messages between all routers in my AS (288 times in this case): 14:19:26.018478 109.xxx.yyy.11 109.xxx.yyy.12 BGP UPDATE Message Withdrawn prefix: 187.120.96.0 (187.120.96.0) 14:19:26.018567 109.xxx.yyy.12 109.xxx.yyy.11 BGP UPDATE Message Withdrawn prefix: 187.120.96.0 (187.120.96.0) 14:19:26.018643 109.xxx.yyy.11 109.xxx.yyy.12 BGP UPDATE Message NLRI prefix: 187.120.96.0 (187.120.96.0) 14:19:26.018766 109.xxx.yyy.12 109.xxx.yyy.11 BGP UPDATE Message NLRI prefix: 187.120.96.0 (187.120.96.0) If i undestant correctly, ebgp peer .189 withdraw this route, but route is still available via ebgp peer .190 and via ibgp peer and it looks bird don't know which path use. This is one concrete case, but i think, bird have this behaviour with almost of all bgp updates, which i can see in debug log. Thanks for any help. Dan Rimal