[c-nsp] Default routes, OSPF zones, and BGP

[Brandon Ewing]

Greetings,

I'm currently in the process of integrating 3 multi-area OSPF sites with
customer routes in OSPF, moving towards putting all customer routes in BGP
and merging the OSPF area 0s of the sites.  The multi-area setup is NSSA
no-summary for all non-0 areas at each site, as there are several devices
that would probably puke under the full weight of all customer routes
currently.  I'd like some advice from the community regarding default routes
in such an environment.

We're making good strides in getting customer routes into BGP, having
finished all our AS changes, and have all customer routes in BGP at the
first site, ready for the area 0 merge.

While looking at the first site, currently non-area 0 routers receive a
default from area 0 (default-information originate always from core
routers), and this OSPF default route is used by non-area 0 routers to reach
the loopbacks of the aggregation and core platforms.  We'd prefer not to
default-originate in OSPF (tends to install on our core routers with full
tables), but if we remove it, the access routers will lose their route to
the aggregation/core layer (as area 0 loopback interface LSAs aren't going
into non-0 areas).

What's the best approach here?  Should we just leave the OSPF default in
until we get our total OSPF route count low enough to eliminate seperate
areas?  Should we redistribute lo0 /32s into OSPF to make them external
routes that will have LSAs in the non-0 areas? 

Any feedback, suggestions, or other approaches would be appreciated.

-- 
Brandon Ewing                                        (nicotine at warningg.com)
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