[j-nsp] multiple bgp routing tables

Ying Zhang cynthia_dal at yahoo.ca
Thu Nov 6 08:52:06 EST 2008


Just curious, if use "filter-based forwarding" with multiple bgp routing 
tables from multiple ISPs, in case ISP-1 peer is down, will the other ISPs 
become backup links for these prefixes used to destine to ISP-1?

Thanks.
----- Original Message ----- 
From: "Boyd, Benjamin R" <Benjamin.R.Boyd at windstream.com>
To: <truman at suspicious.org>; "John T. Yocum" <john at fluidhosting.com>; 
<juniper-nsp-bounces at puck.nether.net>; <juniper-nsp at puck.nether.net>
Sent: Wednesday, November 05, 2008 6:37 PM
Subject: Re: [j-nsp] multiple bgp routing tables


> >Use communities or prefix lists that restrict the
>>advertisement of specific prefixes for each bgp group/peer.
>>
>>Local pref the received routes from the neighbours that you prefer ...
>>
>>
>>
>
> I think the problem you'll find with preffing the routes from particular
> neighbors is the fact that you don't want to limit by destination.  I
> think he "prefers" all neighbors, but only wants the "special" blocks
> he's advertising to his neighbors to only use those sessions as transit
> regardless of destination.  For this he will need filter-based
> forwarding (aka Source Based Routing).  I've done this in places and
> this document really helped:
>
> http://cn.juniper.net/solutions/literature/white_papers/552003.pdf
>
> -Ben
>
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