Dual Homed BGP

Fri Jan 24 21:45:05 UTC 2020

On 1/23/20 16:01, Brian wrote:
> Hello all. I am having a hard time trying to articulate why a Dual Home 
> ISP should have full tables. My understanding has always been that full 
> tables when dual homed allow much more control. Especially in helping to 
> prevent Async routes.

If you're multi-homed you'll have some asymmetric routes. Even if you 
aren't, they'll be asymmetric to your upstream. It's easy to manipulate 
which path traffic leaving your site takes, difficult or impossible to 
manipulate via which path it enters.

If you have sufficient horsepower and memory in your routers, taking 
full tables won't hurt anything and will help in situations where one of 
your upstreams loses reachability to a destination. For 
belt-and-suspenders, take full routes plus a default.

> Am I crazy?

Perhaps, but if so it has little if any relationship to the size of the 
BGP tables in your border routers.

-- 
Jay Hennigan - jay at west.net
Network Engineering - CCIE #7880
503 897-8550 - WB6RDV