(Routing-101) Protocol redistribution question BGP into OSPF

Tue Jun 15 18:12:52 UTC 2004

Working on what I thought was going to be an easy solution - but hey...

Have 2 campus networks with 2 different autonomies now joined together.  
As an initial step we will leave the different autonomies and try to glue 
them together.  Each campus has a distinct OSPF network and each campus
has separate BGP peering sessions with unique AS's at it's borders.

What we are trying to do is this.  The campuses are connected via 2 PtP
circuits that are internal to each campus.  We have established separate
BGP peering on each circuit - completely distinct from one another.  We 
chose iBGP because of some 3rd party sites that are dual homed to each 
campus, local-pref seemed to be the best way to deal with route 
preference.

So each site is using the same ASN on these internal iBGP sessions. But
there are 2 main peering routers and at each campus (i-e: not a full mesh
but 2 separate iBGP instances).  The routers on the same campus do not
peer with one another.  Rather each router in addition to the BGP session
is an ASBR into a common OSPF area on each campus. The thought is that the
routes learned from iBGP will be redistributed and weighted via OSPF into
the local campus WAN.  There are 3 entry points into each LAN from a 
BGP/OSPF transition - each is independent of the other and each will 
originate default into OSPF.

Now the quandary is this - how to get the campus routes to exchange from
BGP - to OSPF and back again - *without enabling* "redistribute internal"
on BGP.  A few of us are/were of the opinion that once the routes are
populated in the routing table from BGP - the OSPF instance would then
re-advertise them since they are valid routes (of course with a specific
network statement in OSPF) but practice is telling us that this is not
working.  The only way we can get this working at all is by enabling 
"redistribute internal" in BGP and then redistributing BGP in OSPF 
with a route filter. 

Does anyone have something similar working with a method differing from 
"redistribute internal" in BGP.

Please contact me off-list.

-- 
Rich Sena - ras at thick.net
ThickNET Consulting
"On the way to understanding; you understand, and forget."