bgp as-path info

I just brought up a BGP session with one of my providers, they are stripping
our AS as it leaves their network, so it looks like the route is originating
from their network. I have another provider that I will be bringing up BGP
with later this week. Once I bring up the other provider, I will be
advertising several networks out both of them.

Is this as-path stripping going to cause issues? Does it matter either way?


If you look closely, they are probably not just stripping your AS. They are probably aggregating your network. One provider that I am aware of that does this is AT&T. Since your advertisements out the other network will be more specific, traffic will only come through them. If the networks are the same size, then traffic will most likely come through your first provider due to AS path counts.

Usually, you have to request that your more specific routes be allowed out due to multi-homing. In the case of AT&T, they have a community that you must send with the route to have it sent beyond their local network. It's really just a matter of default preference on the part of your provider. Some default to advertise more specific while others default to advertising their aggregates. The latter is used most commonly when a provider does a lot of BGP peering that is not multi-homed. It's not a bad policy when it comes to looking at the BGP tables.


Austad, Jay wrote: