[61680] in North American Network Operators' Group
RE: bgp as-path info
daemon@ATHENA.MIT.EDU (Ejay Hire)
Wed Sep 3 11:23:04 2003
Date: Wed, 3 Sep 2003 10:21:42 -0500
From: "Ejay Hire" <ejay.hire@isdn.net>
To: <nanog@merit.edu>
Errors-To: owner-nanog-outgoing@merit.edu
IIRC, They will advertise your specifics if you attach a community of
7018:20 to the route as you send it to them. Otherwise they aggregate
all of the routes in the 12/8.
-Ejay
-----Original Message-----
From: Austad, Jay [mailto:JAustad@temgweb.com]
Sent: Tuesday, September 02, 2003 1:19 PM
To: 'Jack Bates'; Austad, Jay
Cc: nanog@merit.edu
Subject: RE: bgp as-path info
Actually, it looks like this is what they are doing. I've already put a
call in with them.
> -----Original Message-----
> From: Jack Bates [mailto:jbates@brightok.net]
> Sent: Tuesday, September 02, 2003 1:17 PM
> To: Austad, Jay
> Cc: nanog@merit.edu
> Subject: Re: bgp as-path info
>=20
>=20
> If you look closely, they are probably not just stripping=20
> your AS. They=20
> are probably aggregating your network. One provider that I am=20
> aware of=20
> that does this is AT&T. Since your advertisements out the=20
> other network=20
> will be more specific, traffic will only come through them. If the=20
> networks are the same size, then traffic will most likely=20
> come through=20
> your first provider due to AS path counts.
>=20
> Usually, you have to request that your more specific routes=20
> be allowed=20
> out due to multi-homing. In the case of AT&T, they have a=20
> community that=20
> you must send with the route to have it sent beyond their=20
> local network.=20
> It's really just a matter of default preference on the part of your=20
> provider. Some default to advertise more specific while=20
> others default=20
> to advertising their aggregates. The latter is used most=20
> commonly when a=20
> provider does a lot of BGP peering that is not multi-homed.=20
> It's not a=20
> bad policy when it comes to looking at the BGP tables.
>=20
> -Jack
>=20
> Austad, Jay wrote:
>=20
> > I just brought up a BGP session with one of my providers,=20
> they are stripping
> > our AS as it leaves their network, so it looks like the=20
> route is originating
> > from their network. I have another provider that I will be=20
> bringing up BGP
> > with later this week. Once I bring up the other provider, I will be
> > advertising several networks out both of them.
> >=20
> > Is this as-path stripping going to cause issues? Does it=20
> matter either way?
> >=20
> > -jay
>=20
>=20
>=20
