[c-nsp] Conditional BGP

[Jon Lewis]

On Tue, 23 Sep 2008, Paul Stewart wrote:

> We have a couple of customers that are looking to purchase an Internet
> connection from us - this will be a BGP feed to each customer as they are
> multihomed today etc.
>
> Normally, we would just supply a full table and let them decide what to do
> with it.  In this scenario, they both wish to use us as a backup provider
> and wish to ONLY use our network if their primary provider (Cogent) is down.

I wouldn't call this conditional BGP.  We have a few customers doing this, 
and in most cases they do this because they don't have big enough routers 
to handle multiple full bgp tables.

The typical setup is to use route-maps to set localpref on received routes 
(making the primary provider's route(s) preferred) and on sent routes to 
do several prepends to make the backup path less preferable to the 
internet.  In such a setup, the customer probably doesn't need more than 
default routes from each provider.

----------------------------------------------------------------------
  Jon Lewis                   |  I route
  Senior Network Engineer     |  therefore you are
  Atlantic Net                |
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