BGP convergence

Unanswered Question
Mar 28th, 2007
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Hello,


I have one upstream provider, and that upstream provider is connected to internet with two routers (and also two ISP's). When one of that upstream ISP routers is down I lose connectivity for 4 minutes to internet. What is convergence time for BGP?(what is the time that new routes is active on my router after one of upstreams router is down).4 minutes seems to much.


Thanks in advance

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Overall Rating: 5 (3 ratings)
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lawjen821 Wed, 03/28/2007 - 03:29
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Cisco default keepalive and hold timers is 60 and 180 seconds. Usually the provider is not going to advice from the customer, but it looks like they might have to adjust their upstream sessions BGP timers.

royalblues Wed, 03/28/2007 - 05:06
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You can slightly reduce the convergence time by adjusting the BGP timers at your end.

THe BGP neighbors negotiate these timers during the initial state and choose the lowest one.

router bgp 100

neighbor x.x.x.x remote-as 200

timers 3 9


However as posted above, you cannot control the convergence time between your ISP and their upstream providers


HTH, rate if it does

Narayan

IVAN PEPELNJAK Wed, 03/28/2007 - 23:32
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The "180 seconds" give you three minutes. Then there's the delay before the router sends out the updates (neighbor advertisement-interval, up to 30 seconds by default on EBGP, 5 seconds on IBGP) and before the incoming BGP updates are considered for inclusion in the IP routing table.


But, as said before, these timers have to be tweaked by your ISP, there's nothing you can do.

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