BIRD - iBGP between both RS - invalid NEXT-HOP notification.

7 Mar 2014

      Hello,

We use BIRD as route server for a long time without any problems. We 
have both fully symmetric RS for redundancy.

Yesterday we decided to establish "internal BGP session" between both of 
them. The reason to do this is to achieve prefix symmetric on both RS. 
Some of our members hold BGP session only with one of our route servers.

But after establishing this BGP session we began to see the following 
message into our logs on both RS for total random prefixes on absolutely 
random intervals.

Here is part of my bird.log:
07-03-2014 14:19:41 R0_29: Invalid NEXT_HOP attribute in route 
178.254.232.0/21
07-03-2014 14:19:41 R0_30: Invalid NEXT_HOP attribute in route 
178.254.232.0/21
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.156.0/22
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.148.0/22
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.144.0/20
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.152.0/22
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.144.0/22
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.156.0/22
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.144.0/20
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.148.0/22
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.152.0/22
07-03-2014 14:18:52 R0_52: Invalid NEXT_HOP attribute in route 
79.140.144.0/22
07-03-2014 14:16:39 R0_29: Invalid NEXT_HOP attribute in route 
178.254.232.0/21
07-03-2014 14:16:39 R0_30: Invalid NEXT_HOP attribute in route 
178.254.232.0/21
07-03-2014 14:01:39 R0_52: Invalid NEXT_HOP attribute in route 
95.168.66.0/23
07-03-2014 14:01:39 R0_52: Invalid NEXT_HOP attribute in route 
95.168.68.0/23
07-03-2014 13:52:02 R0_14: Invalid NEXT_HOP attribute in route 
151.252.198.0/24
07-03-2014 13:51:57 R0_14: Invalid NEXT_HOP attribute in route 
151.252.198.0/24
07-03-2014 13:29:36 R0_87: Invalid NEXT_HOP attribute in route 
85.11.144.0/20
07-03-2014 13:29:28 R0_87: Invalid NEXT_HOP attribute in route 
85.11.144.0/20
07-03-2014 13:29:15 R0_87: Invalid NEXT_HOP attribute in route 
85.11.144.0/20
07-03-2014 13:29:06 R0_87: Invalid NEXT_HOP attribute in route 
85.11.144.0/20
07-03-2014 13:28:14 R0_87: Invalid NEXT_HOP attribute in route 
85.187.120.0/22
07-03-2014 13:28:14 R0_87: Invalid NEXT_HOP attribute in route 
85.187.120.0/22
07-03-2014 13:19:36 R0_87: Invalid NEXT_HOP attribute in route 
85.187.120.0/22
07-03-2014 13:19:31 R0_87: Invalid NEXT_HOP attribute in route 
85.187.120.0/22
07-03-2014 13:19:31 R0_87: Invalid NEXT_HOP attribute in route 
85.11.144.0/20
07-03-2014 13:19:31 R0_87: Invalid NEXT_HOP attribute in route 
85.187.120.0/22
07-03-2014 13:19:22 R0_87: Invalid NEXT_HOP attribute in route 
85.11.144.0/20
07-03-2014 13:13:43 R0_71: Invalid NEXT_HOP attribute in route 
46.229.194.0/24
07-03-2014 13:13:43 R0_71: Invalid NEXT_HOP attribute in route 
46.229.192.0/23
07-03-2014 13:13:42 R0_29: Invalid NEXT_HOP attribute in route 
46.229.194.0/24
07-03-2014 13:13:42 R0_29: Invalid NEXT_HOP attribute in route 
46.229.192.0/23
07-03-2014 13:06:22 R0_60: Invalid NEXT_HOP attribute in route 
193.104.73.0/24
07-03-2014 13:03:54 R0_52: Invalid NEXT_HOP attribute in route 
178.79.61.0/24
07-03-2014 12:54:56 R0_60: Invalid NEXT_HOP attribute in route 
89.35.114.0/24
07-03-2014 12:54:56 R0_60: Invalid NEXT_HOP attribute in route 
86.105.150.0/24
07-03-2014 12:54:56 R0_60: Invalid NEXT_HOP attribute in route 
46.102.181.0/24
07-03-2014 12:54:56 R0_60: Invalid NEXT_HOP attribute in route 
46.102.176.0/24
07-03-2014 12:54:56 R0_60: Invalid NEXT_HOP attribute in route 
37.156.69.0/24
07-03-2014 12:54:25 R0_60: Invalid NEXT_HOP attribute in route 
188.240.70.0/24
07-03-2014 12:54:25 R0_60: Invalid NEXT_HOP attribute in route 
188.212.157.0/24
07-03-2014 12:34:43 R0_52: Invalid NEXT_HOP attribute in route 
91.148.106.0/24
07-03-2014 12:27:48 R0_52: Invalid NEXT_HOP attribute in route 
91.148.118.0/24
07-03-2014 12:16:33 R0_29: Invalid NEXT_HOP attribute in route 
178.254.232.0/21
07-03-2014 12:16:33 R0_30: Invalid NEXT_HOP attribute in route 
178.254.232.0/21
07-03-2014 12:09:39 R0_87: Invalid NEXT_HOP attribute in route 
85.11.144.0/20
07-03-2014 12:09:10 R0_87: Invalid NEXT_HOP attribute in route 
85.11.144.0/20
07-03-2014 12:08:57 R0_87: Invalid NEXT_HOP attribute in route 
85.187.120.0/22
07-03-2014 12:08:50 R0_87: Invalid NEXT_HOP attribute in route 
85.187.120.0/22
07-03-2014 12:08:49 R0_87: Invalid NEXT_HOP attribute in route 
85.187.120.0/22
07-03-2014 12:02:41 R0_52: Invalid NEXT_HOP attribute in route 
212.200.0.0/21
07-03-2014 11:47:01 R0_29: Invalid NEXT_HOP attribute in route 
178.254.232.0/21
07-03-2014 11:47:01 R0_30: Invalid NEXT_HOP attribute in route 
178.254.232.0/21
07-03-2014 10:55:50 R0_60: Invalid NEXT_HOP attribute in route 
91.206.209.0/24

I had checked many times and make many tests if the next-hop is correct 
and everything looks
fine but this messages  comes permanently :)

We managed to troubleshoot the following behavior and relationship and 
see the following effect:

Our scenario:

0.100                 0.200
RS1 <- iBGP -> RS2
   |                       |
   |                       |
TEST.AS -----------
0.252

TEST.AS announce: 31.13.244.0/24

RS2 learn this prefix as:

31.13.244.0/24     via 10.1.0.252 on eth0 [R0_252 14:44] * (100) [AS60230i]
                              via 10.1.0.252 on eth0 [*R0_100* 15:12 
from 10.1.0.100] (100) [AS60230i]

As soon as we stop to announce 31.13.244.0/24 from TEST.AS to RS1, in 
the logs of RS1 begin to come the following message:

07-03-2014 15:10:09R0_252: Invalid NEXT_HOP attribute in route 
31.13.244.0/24

But when we try to shutdown (administratively ) the session between 
TEST.AS and RS1 this behavior does not occur and everything seems normal.

I hope this information will be useful for resolving this strange issue.

Here is our configuration set on both RS. The real AS number & IPs has 
been changed for security reason :)

# RS2:
table T65535

protocol pipe P65535 from iBGP_PIPES {
   description "RS1";
   peer table T65535;
   export where RS_PIPE_OUT();
}

protocol bgp R0_100 from iBGP {
   description "0.100_iBGP_RS1";
   source address 10.1.0.200;
   neighbor 10.1.0.100 as 65535;
   import all;
   export all;
   passive off;
   table T65535;
   route limit 10000;
   gateway direct;
}

# RS1:
table T65535

protocol pipe P65535 from iBGP_PIPES {
   description "RS2";
   peer table T65535;
   export where RS_PIPE_OUT();
}

protocol bgp R0_200 from iBGP {
   description "0.200_iBGP_RS1";
   source address 10.1.0.100;
   neighbor 10.1.0.200 as 65535;
   import all;
   export all;
   passive off;
   table T65535;
   route limit 10000;
   gateway direct;
}

# show bgp summary shows the following:
# RS2:
---------------------------------------------------------------- adv / 
rcv / limit ---
0.100_iBGP_RS1    10.1.0.100    65535    Mar06    Established 
4527/3235/10000
--------------------------------------------------------------------------------------

# RS1:
---------------------------------------------------------------- adv / 
rcv / limit ---
0.200_iBGP_RS2    10.1.0.200    65535    Mar06    Established 
3235/4527/10000
--------------------------------------------------------------------------------------

Any ideas or thoughts are highly appreciated!

Thanks in advance!

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*Javor Kliachev*
IP Engineer

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