BGP Migration to another Provider

stephen.stack · ‎07-30-2008

Hi,

I have been tasked with changing our primary BGP path to another provider.

We have an two edge routers at different NAPs and both are peered with many other ISPs through the NAPs network. However, we use two primary tier 1 ISPs for our primary and secondary paths.

At one NAP we are connecting up with a new provider, and retaining the old one until the contract expires.

I am looking for some tips on the migration process. The idea is to use the new provider as our primary path. with all other peers for shortest paths to respective AS's.

How much downtime, and flapping will be caused by doing this. Anyone who has done this before, what are the gotchas.

Thanks a mil

Stephen

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Giuseppe Larosa · ‎07-30-2008

Hello Stephen,

you can follow some steps:

a) setup the eBGP session to the new provider

advertise your IP prefixes to this neighbor

Use a public looking glass to verify the correct propagation of your advertisements or have the new provider's feedback

b) verify you are receiving a BGP full table from the new provider just use sh ip bgp summary and compare the number of prefixes receveid by the old and by the new provider

they don't need to match but to be of the same order

note: to do this you need to verify that you have at least 100 MB of free memory on your router to hold all the prefixes you receive in the new eBGP session

c) after all checks you can provide preference to the new provider for outgoing traffic

note: until you have the eBGP session with the old provider you have limited influence on the return path you can just prepend your own AS number in your advertisements to old provider

Hope to help

Giuseppe