Cisco ASA Supports Two OSPF Processes

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.

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