[c-nsp] Non-transit ospf routes

[Ross W]

I'm looking at setting up a blackhole router via ospf (not bgp) and
attaching it to multiple connections.  But I don't want it to be possibly
used as a transit path in case something happens.

The quick diagram would be the classic triangle:  rtrA connects to rtrB +
rtrC, which are interconnected at a high speed.

Basically I'm looking at a way of forcing rtrB + rtrC to not even consider
the path of rtrB - rtrA - rtrC in case the rtrB-rtrC link were to fail (as
there are other better paths not illustrated).  I realize that you can set
the cost to be hugely higher on the A-B, A-C links, but that still doesn't
eliminate the possibility of transiting rtrA in case something happens.

I see that the "area <x> filter-list prefix <list> (in|out)" command works
with type 3 routes, but if I were to redistribute static (ie: "ip route
a.b.c.d w.x.y.z null0") routes, they'll show up as type 5, and therefore not
filtered.

Is the only solution to run multiple ospf processes on the router (one per
link basically) and do it that way, or does anyone know of a better
solution?