[c-nsp] PBR and BGP Question

[Pete S.]

How are you getting the default route into your core?

If your ISP border routers, and core are running iBGP, simply use the
local preference variable in BGP to send out the prefered ISP.   If
that ISP connection goes down, the next highest local pref will become
the default.

Depending on the routes you're receiving, and redistributing...If
you're redistributing your BGP into an IGP, you can announce two
default routes into your IGP, one with a higher metric, from each
border router running BGP.  in case of ISP failure, your traffic will
get up to the ISP border routers, and then hopefully have a more
specific route between iBGP, if one ISP connection were down.  Traffic
would then take its course back to the ISP border router with the
active ISP connection.

You can also play with EEM(I can't recall if its in the Sup1 or 2, but
I'd wager no) to pull the default route from the isp border router, if
the BGP session were to drop on that router, and then re-insert it
when BGP session reconnects.

--Pete

On Jan 21, 2008 1:28 PM, Jason Ford <jason at chatinara.com> wrote:
> All,
>
> I have a need to direct traffic from within our core routers out a
> specific BGP peer unless that peer is down. Here is the setup..
>
> customer network ---> core router 03 and core router 04 --------> border
> router 01 and border router 02 ---------> our bgp peers..
>
> Basically, the customer is connected to two 6500's running eigrp
> sessions with the border routers. The border routers are running BGP and
> eigrp. Border router 01 has a BGP connection to ISP A and Border router
> 02 has a BGP connection to ISP B.  All routers are meshed together via
> GE. Core Routers are 6500's with sup1a/msfc2's fully upgraded with
> memory (yeah.. I know it should be upgraded to a sup2) and the border
> routers are 6500's with sup2/msfc2 also fully upgraded with memory.
>
> Ok, here is the question. If we would like to route all of the
> customer's traffic out ISP B unless it is down, is a PBR on the border
> routers identifying the source address and setting a next hop the best
> way of doing this? We don't care which ISP the incoming traffic goes to
> but want to control the outgoing traffic.
>
> Hopefully that gets the question across without a network diagram.
>
> Thanks for all who read and respond.
>
> jason
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