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New Member

Router is dropping IBGP peer session


Recently, I noticed that our router is dropping IBGP session time to time. It happens once in two to three days. I'm not really sure if our hardware went bad or we have a configuration problem.

Interface it looks ok(no error), CPU utilization is low and proc memory status looks fine too.

Any suggestion or comment would really be appreciated.

Thank you


PS. Here is "show logging" output,

Router1(Cisco 7500)

cisco7500r#sho logging | i BGP

Sep 20 09:31:11: %BGP-5-ADJCHANGE: neighbor Down BGP

Notification sent

Sep 20 09:31:11: %BGP-3-NOTIFICATION: sent to neighbor 4/0

(hold time expired) 0 bytes

Sep 20 09:31:23: %BGP-5-ADJCHANGE: neighbor Up

Router2(foundry netIron400)

telnet@netIron# sho log

Syslog logging: enabled (0 messages dropped, 0 flushes, 1 overruns)

Buffer logging: level ACDMEINW, 50 messages logged

level code: A=alert C=critical D=debugging M=emergency E=error

=informational N=notification W=warning

Dynamic Log Buffer (50 lines):

14d20h49m03s:N:BGP Peer UP (ESTABLISHED)

14d20h48m51s:N:BGP Peer DOWN (Rcv Notification:Hold Timer



Re: Router is dropping IBGP peer session

BGP timers are 60 sec keepalive and 180 sec hold time. Is other traffic interferred with during this time? By your post peers didn't receive hello for 192 seconds.

Do a show ip bgp neighbor x.x.x.x to see reason why it flapped.

Check your mtu (with an extended ping) between peers and correct if necessary by set ip mtu.

Try this with caution (based on load of routers etc) -

debug ip bgp x.x.x.x

debug ip bgp keepalives

debug ip bgp events

debug ip tcp transactions

Let us know.


New Member

Re: Router is dropping IBGP peer session

Thanks for your reply, Steve.

No, there isn't any other traffic interferred with BGP session since we aren't running any other routing protocol other then BGP.

"Show ip bgp neighbor xxxx" command showed that it flapped due to BGP notification sent but hold time expired.

"debug ip bgp xxxx updates" and "debug ip bgp keeplives" commands didn't show any suspicious activities or update messages.

"debug ip tcp transactions" command didn't catch any debug messages.

"debug ip bgp evnets" commands showed the following messages,

1w2d: BGP: Import timer expired. Walking from 1 to 1

1w2d: BGP: Import timer expired. Walking from 1 to 1

1w2d: BGP: Performing BGP general scanning

1w2d: BGP(0): scanning IPv4 Unicast routing tables

1w2d: BGP(IPv4 Unicast): Performing BGP Nexthop scanning for general


1w2d: BGP(1): scanning VPNv4 Unicast routing tables

1w2d: BGP(VPNv4 Unicast): Performing BGP Nexthop scanning for general


1w2d: BGP(2): scanning IPv4 Multicast routing tables

1w2d: BGP(IPv4 Multicast): Performing BGP Nexthop scanning for general


1w2d: BGP: Import timer expired. Walking from 1 to 1

I don't think I would see any errors or suspicious activities at this moment since BGP session between peers is running fine.

I guess I'll have to wait until it flaps again.

Thank you

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