I've got a strange problem. Here is the set up below:
6500 running OSPF and switching at site A
6500 running OSPF and switching at site B
3750 L3 switch running OSPF at site C
Router A and B have both an OSPF connection and a L2 trunk running between them (this is needed as there's lots of legacy stuff still running on common vlans). This seems to work fine and clients on site B are able to reach everything.
However, added new router C through OSPF to router B. Clients on Router B are then unable to reach anything on vlan X (a common vlan). Take the router C out of the equation and everything works again.
How can just adding a new network in to OSPF cause this? I would have thought if it's a routing/bridging conflict it would be happening all the time.