[c-nsp] Dual-homing scenario

[David Prall]

Do an inbound route-map on the ISP 1 connection to drop all but local AS or
something you like. Do not accept a default from ISP 1. Put in a static
default pointing to one of the routes you are accepting from ISP 1 with a
high distance so it only goes in if the default from ISP 2 goes away, and
the route is available from ISP 1. You could do some EOT stuff to make this
backup static a little more reliable if you wished. For return traffic, I
would find out if ISP 1 has community based prepending, so that they prepend
on their exit.

David

--
http://dcp.dcptech.com


> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
> Vincent De Keyzer
> Sent: Thursday, February 22, 2007 7:37 AM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Dual-homing scenario
>
> Hello,
>
>
>
> let a dual-home BGP network. ISP1 comes in with a T3 and
> sends a full BGP table; ISP2 comes with a FE and a
> default-route (for memory reasons).
>
>
>
> ISP2 is preferrable because of capacity, but ISP1 is
> preferred because any route is more specific than a default
> route; hence all upstream traffic goes to ISP1, which is not good.
>
>
>
> Still, it would be nice to keep sending *some* traffic to
> ISP1; but most of the traffic should go to ISP2.
>
>
>
> One way I see to achieve this would be to local-pref based on
> AS path: if the route comes from ISP1's AS, or from an AS
> directly connected to ISP1, local-pref it with 130; else
> local-pref it with 100 (and local-pref the default route from
> ISP2 with 120).
>
>
>
> Is this a good way to do it?
>
>
>
> Take into account that ISP1 is not very flexible (and ISP2 is
> flexible, but likes simple things). :-)
>
>
>
> Vincent
>
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