BGP Confederation peer weirdness, 12.0 and 12.1 don't mix.

From: Jon Carmichael (jonc@xxxxxxxxxxx)
Date: Tue Aug 14 2001 - 21:21:00 GMT-3


   
I just today caught a strange discrepancy between version 11.2, 12.0 and
12.1.

Originally all my routers within a confederation were configured similar to
the following...

router bgp 43
  bgp confederation identifier 20
  bgp confederation peers 42 44

But when configured as such, --there was a router external to the
confederation that was getting the error that looks like..

%BGP-6-ASPATH: Invalid AS path (43) 18 17 received from 172.20.100.1: Non
confederation peer

So I figured I would fix that by including the AS number of the border
router to the confederation with a change that puts 'his' autonomous system
number in the list of peers, -so that after the fix the config now looks
like...

router bgp 43
  bgp confederation identifier 20
  bgp confederation peers 42 43 44

I did this on all the routers, --three of them running 12.0 and one running
11.2, and it worked, the error popping up on the next door AS stopped. But
while I was running around to all the border routers trying to make the
similar config change, one of them popped up with an error while configuring
telling me you can't do that. --Paste of the config change attempt is
below. Turns out that 11.2, 12.0 will let you, --in fact in 12.0 you
*must* or a router in a next-door AS will complain if you don't and in 12.1
you can't!

Example while making the change in 12.1 follows.

Not a question, --just a curious discrepancy between different versions of
the code.

JONC

router bgp 43
 no synchronization
 no bgp log-neighbor-changes
 bgp confederation identifier 20
 bgp confederation peers 42 44
 network 172.20.101.1 mask 255.255.255.255
 timers bgp 3 9
 neighbor 172.17.100.1 remote-as 17
 neighbor 172.17.100.1 ebgp-multihop 2
 neighbor 172.17.100.1 update-source Loopback0
 neighbor 172.18.100.1 remote-as 18
 neighbor 172.18.100.1 ebgp-multihop 2
 neighbor 172.18.100.1 update-source Loopback0
 neighbor 172.20.100.1 remote-as 43
 neighbor 172.20.100.1 update-source Loopback0
 no auto-summary
!
no ip classless
ip route 172.17.100.1 255.255.255.255 192.168.255.81
ip route 172.18.100.1 255.255.255.255 192.168.255.82
no ip http server
!
Fremont#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Fremont(config)#router bgp 43
Fremont(config-router)#bgp confed peers 42 43 44
% Local member-AS not allowed in confed peer list
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