[j-nsp] Generating routes from inactive/hidden contributors

[Tore Anderson]

Hi,

* adamv0025 at netconsultings.com

> Interesting, 
> There appears to be no cmd to override the default, "contributing route has
> to be active", requirement. (the "from state inactive" attachment point is
> only the export policy). 
> I'm just thinking whether it's not working simply because the inactive
> routes wouldn't be advertised anyways -so why to bother aggregating them
> right? 

True, but this is a generated route, not an aggregated route. They're
quite similar, but the generated routes can have next-hops (copied from
a contributing route), which means you don't really need the
contributing routes themselves to be active or even non-hidden to
actually forward packets somewhere useful.

Aggregated routes are on the other hand discard only, so then you need
the more-specific contributing routes with their next-hops to avoid
blackholing traffic.

(AIUI, anyway.)

> But maybe if you enable "advertise-inactive" towards your iBGP -maybe
> then the aggregation starts to work? 

Perhaps, but if both the generated route and its contributors are
indeed inactive in the RIB and thus not found in the FIB, then I don't
think the router would be able to forward the packets it attracts to
where it should.

> Alternatively, I'm thinking of something along the lines of making the
> prefixes active (to allow the aggregate to be advertised), but use
> them only for routing not for forwarding -so that FIB on a local
> router is not skewed.

Yep, something like that would probably do the trick. I was hoping to
keep them out of the RIB in the first place though, to avoid having to
explicitly filter them on export to the FIB and iBGP peers, but maybe
there's no way around it.

Tore