Sometimes, thinking too much stops you from checking the basics. I have often wished that the Cisco ASA supported more than one routing process like the Juniper Netscreen does (which does this brilliantly). Why didn’t I look for this sooner ?-
The security appliance can run two processes of OSPF protocol simultaneously, on different sets of interfaces. You might want to run two processes if you have interfaces that use the same IP addresses (NAT allows these interfaces to coexist, but OSPF does not allow overlapping addresses). Or you might want to run one process on the inside, and another on the outside, and redistribute a subset of routes between the two processes. Similarly, you might need to segregate private addresses from public addresses.
You can redistribute routes into an OSPF routing process from another OSPF routing process, a RIP routing process, or from static and connected routes configured on OSPF-enabled interfaces.
This is a kewl feature and allows for some fancy routing capabilities.
router ospf 1 network 192.168.1.0 255.255.255.0 area 0 area 0 authentication message-digest log-adj-changes redistribute ospf 2 metric 100 subnets ! router ospf 2 network 192.168.2.0 255.255.255.0 area 0 area 0 authentication message-digest log-adj-changes redistribute ospf 1 metric 100 subnets
A related article Why Two Routing Processes as requested by Christian in the comments.