[c-nsp] Redundant default route, without round-robin routing

[Dario]

Dear all,

I've configured something similar a few days ago with one customer running OSPF
as internal protocol.

We've installed two links between us and the customer (two different border routers),
one acting as backup (only active when the main one fails).

We've configured two BGP sessions with each of the customer routers, using local 
preference to prefer the main link. Also the customer uses local preference to prefer
the main link. We only advertise default route and we receive all the customer 
routes (the customer forces the advertisement using static routes to null with a 
poor metric).

Inside the customer it's configured an iBGP session between the two border routers
in order to pass the default route between them. Then, each border router receives 
the default route via eBGP (from us) an iBGP (from the other border router). With 
the local preference, the main link is prefered.

The defaul route inside the customer is distributed in the OSPF cloud using
"default-information originate allways".

At normal situation the main link is used: all traffic inside the OSPF cloud reach 
one of the border routers, and then the border router send it directly to us or (if it's 
the backup one) to the other border router.

If the main link fails all customer traffic flow to the backup border router and then 
to us.

The solution works fine ;)!

Regards,

	Dario D.


El Jueves, 27 de Septiembre de 2007 17:05, Jon Lewis escribió:
> On Thu, 27 Sep 2007, Vincent De Keyzer wrote:
> 
> > I was thinking of having both BGP routers advertising a default route in
> > OSPF; but in this case, in order to limit packet out-of-sequence problems, I
> > want to make sure that every IP flow uses the same default gateway.
> 
> Have you tried having one of the eBGP routers originate a default route 
> into OSPF using a different metric than the other?
> 
> #default-information originate ?
>    always       Always advertise default route
>    metric       OSPF default metric
>    metric-type  OSPF metric type for default routes
>    route-map    Route-map reference
> 
> ----------------------------------------------------------------------
>   Jon Lewis                   |  I route
>   Senior Network Engineer     |  therefore you are
>   Atlantic Net                |
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