From: Kenneth Wygand (KWygand@customonline.com)
Date: Tue Jun 22 2004 - 00:58:48 GMT-3
Hey Tim,
Do you have access to the configurations on BB1? Do you know what BGP routes BB1 is sending you?
Also, how do you know how to reach 54.6.7.254 and 54.6.8.254? How are you learning these?
If you don't have access to the BB1 configs, perhaps you can "debug ip routing" and see if the routes you are getting from your BB1 is causing the problem. For example, if you are learning how to reach 54.6.7.254 and 54.6.8.254 through BGP, those routes probably have a lower (20) AD through EBGP and might be bumping your IGP routes from your routing table. Similar to the "can't reach the destination of a tunnel through the tunnel interface" problem, you might be trying to get maintain connectivity to your BGP neighbor through BGP-learned routes. This could be causing your disconnection / reconnection after your IGP becomes the best route again when BGP leaves.
By the way, if this is the case, the BGP BACKDOOR feature was created to solve this issue. Take a look at the following link:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123tcr/123tip2r/ip2_n1gt.htm#wp1084394
Good Luck!
Ken
-----Original Message-----
From: nobody@groupstudy.com on behalf of ccie2be
Sent: Mon 6/21/2004 11:40 PM
To: Group Study
Cc:
Subject: BGP flapping
Hi Guys,
This has been bothering me most of today. I just can't figure it out.
I'm doing a practice lab and R6 has 2 pppoATm connections to BB1. The configs
are shown below.
Aside from BGP, there aren't any other routing protocols running between R6
and BB1.
I tried using ( and not using) nei... ebgp multihop and the same for nei ...
update-source lo0.
Nothing seems to make any difference. The BGP session just keeps flapping up
and down.
Anyone know what's going on here? If so, please tell me what I should do to
correct this annoying problem.
Thanks kindly, Tim
interface ATM1/0
no ip address
no atm ilmi-keepalive
pvc 0/16 ilmi
!
!
interface ATM1/0.206 point-to-point
pvc 0/206
--More--
11:50:11: %BGP-5-ADJCHANGE: neighbor 54.6.8.254 Down Peer closed the session
broadcast
encapsulation aal5snap
protocol ppp Virtual-Template1
!
!
interface ATM1/0.306 point-to-point
pvc 0/306
encapsulation aal5snap
protocol ppp dialer
dialer pool-member 1
!
router bgp 100
no synchronization
bgp log-neighbor-changes
network 142.6.40.0 mask 255.255.248.0
neighbor 54.6.7.254 remote-as 54
neighbor 54.6.7.254 ebgp-multihop 255
neighbor 54.6.7.254 update-source Loopback0
neighbor 54.6.8.254 remote-as 54
neighbor 142.6.46.4 remote-as 45
neighbor 204.12.6.3 remote-as 200
neighbor 204.12.6.254 remote-as 54
no auto-summary
--More--
11:51:34: %BGP-5-ADJCHANGE: neighbor 54.6.7.254 Up
--More--
11:51:46: %BGP-5-ADJCHANGE: neighbor 54.6.8.254 Up
--More--
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