BGP Neighbor drop

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May 7th, 2010
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I have a Metro -Ethernet connection to my service provider running BGP.  My BGP session dropped (neighbor) and I am not sure why.  There are no errors on my interface.  There was an increase in traffic at the time it went down, but the link was not completely saturated.  The service provider is stating BGP went down due to congestion on the link, but I do not see any congestion on my end.  Is this possible?  Will BGP drop due to congestion?  Thanks.

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Reza Sharifi Fri, 05/07/2010 - 20:30
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Congestion should not cause a BGP link/peer to drop. 

What does "sh log" shows?



itninja2010 Fri, 05/07/2010 - 21:06
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Thanks for the reply.  Here is the output of my show log when the event occured:

Apr 30 19:27:33.017 GMT: %BGP-5-ADJCHANGE: neighbor "IP" Down BGP Notification sent

Apr 30 19:27:33.017 GMT: %BGP-3-NOTIFICATION: sent to neighbor "IP" 4/0 (hold time expired) 0 bytes

Apr 30 19:30:08.755 GMT: %BGP-5-ADJCHANGE: neighbor "IP" Up

Giuseppe Larosa Sat, 05/08/2010 - 00:54
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Hello IT Ninja,

not all Cisco platforms have a system hidden queue for routing protocol messages you may need to implement a QoS scheduler to provide resources for BGP message exchange.

Ideally you should use hierarchical QoS (two levels) with parent policy shaping all traffic to stated CIR with metro ethernet provider and child policy that implements a queueing system with one queue/class for BGP and other routing  protocols

Congestion may have happened also in service provider network but you should take the above measures on all metroE connected devices.

Hope to help



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