RE: bgp as-path info

["Truman, Michelle, RTSLS" <mtruman () att com>]

Jay,

 Customer care should be able to help you. If you have any trouble let me know. I can tell you the community you need 
to use to get your more specific route out. 

Michelle

Michelle Truman   CCIE # 8098
Principal Technical Consultant
AT&T Solutions Center
mailto:mtruman () att com
Work: 651-998-0949 





-----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
>
>
> 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