Tuning BGP Convergence

[Vinayaka Raman]

Friends,

We have a layer 3 MPLS VPN and each remote site or Data center DC has a local AS of 65457 and remote-as AS as 65000. Provider must be using some as-override. Site A and B are interconnected by P2P link. I did an iBGP between these two sites in order to avail the failover\failback under different DR scenarios. When I shutdown the MPLS connection of Site A, site B router takes more than couple of minutes to realize that the prefix of site A advertised by eBGP peer (provider router) is no more and then it installs the iBGP route.

Is this likely a cause of convergence within the provider cloud or can I improve by tweaking on CE routers itself? Please feel free to ask more details

[blau grana]

Hi

It depends on way how do you shut eBGP session.

By default hello timer is 60s and hold-down timer is 180s == 3min. If PE router needs to wait 3min to withdraw BGP vpnv4 prefixes, you can tune BGP timers to shorter intervals.

You can set BGP timers on one end, BGP session will use shorter timers from both configured.

[Vinayaka Raman]

"It depends on way how do you shut eBGP session."

Thanks for the note... I am seeking further understanding..

I did a admin shut on the Gig interface for testing.. Can you please explain how eBGP tear down in other scenarios would react for convergence ?

Sent from Cisco Technical Support iPad App

[Abzal]

Hi,

Here is you can find a very good information about BGP convergence

http://blog.ine.com/2010/11/22/understanding-bgp-convergence/

Hope it will help.

Best regards,
Abzal