[j-nsp] discard route resolveability in BGP path selection?

[Daniel Roesen]

On Thu, Feb 26, 2004 at 07:30:14PM +0200, Pekka Savola wrote:
> > I don't think there is any ambiguity... any route should be usable for
> > resolution purposes, by default.
> 
> Is there a way to change that behaviour?
> 
> from 9.1.2.1:
> 
>       2. Routes referencing interfaces (with or without intermediate
>       addresses) are considered resolvable if the state of the refer-   
>       enced interface is up and IP processing is enabled on this inter- 
>       face.
> 
> I would consider "discard" as a "null" interface.  Whether such an 
> interface should be "up" or not might be up for debate.  Certainly, it 
> would make a lot of sense to explicitly exclude any discard routes as 
> unresolveable!

I concur. Would be nice and make a whole lot of sense.

> We want to to send only default BGP route to some peers, and we 
> generate that from the discard route.  Any other way to achieve that?
> (Futzing around in documentation indicates that setting these routes, 
> additionally, as 'no-install' might get the behaviour we want.  Is 
> this true?

no-install means that it doesn't get installed in the FIB, but it's
still present in the RIB. As BGP uses RIB for next-hop resolution,
I somewhat doubt that no-install changes anything.

> Any other options?)

AFAIK no. Juniper said that they didn't want to implement special
knobs like default-originate if this can be done by using static
routes and standard policy filtering.

> By the way, is it possible to specify that the routes used for BGP
> resolveability checks must have lower preference than FOO.  That is,
> keeping all the p-t-p and OSPF addresses in OSPF, I'd like to avoid
> the BGP resolvability process considering BGP routes?  

set protocols bgp group foo protocol ospf

This makes next-hop resolution consider only OSPF-learned routes.


Best regards,
Daniel