[61653] in North American Network Operators' Group
RE: bgp as-path info
daemon@ATHENA.MIT.EDU (Austad, Jay)
Tue Sep 2 14:23:44 2003
From: "Austad, Jay" <JAustad@temgweb.com>
To: 'Jack Bates' <jbates@brightok.net>,
"Austad, Jay" <JAustad@temgweb.com>
Cc: nanog@merit.edu
Date: Tue, 2 Sep 2003 13:18:59 -0500
Errors-To: owner-nanog-outgoing@merit.edu
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
>
>
> 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.
>
> -Jack
>
> Austad, Jay wrote:
>
> > 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?
> >
> > -jay
>
>
>
