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Re: Did your BGP crash today?


From: Pierre Francois <pierre.francois () uclouvain be>
Date: Mon, 30 Aug 2010 11:21:42 +0200


Thomas,

Wouldn't the confusion come from the fact that updates are considered as keepalives, so that Claudio sees so few type 4 messages because he receives updates ?

Sec 4.2, Hold Time :

"The calculated value indicates the maximum number of
seconds that may elapse between the receipt of successive
KEEPALIVE and/or UPDATE messages from the sender."

Regards,

Pierre.

Thomas Mangin wrote:
Apart from one big vendor most BGP speaker only send KEEPALIVES when they
need to. So on my full feeds I see sessions running for more then 1 month
which received less then 300 KEEPALIVE packets.


The negociaged holdtime is always the lower value presented between two routers. The default HoldTime timer for Cisco 
is 180 seconds and for Juniper 90.
So you should see a KEEPALIVE packet every minute from/to Cisco routers, and one every 30 seconds between Junipers.

Should a BGP speaker do not see any KEEPALIVE during $HOLDTIME, it will tear the session down.
You are telling me that your effective holdtime is 2592000 seconds when the HOLDTIME field is 16 bits ... hum ...
http://www.faqs.org/rfcs/rfc4271.html section 4.2

So unless you know something I don't, I believe you are totally mistaken :)

Thomas






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