two process on the same interface in ospf

[bharathkumard1994]

I'm running different areas in different OSPF processes.In between R1 and R2 i'm running OSPF process 1 area 1, between R2 and R3 i'm running ospf process 2 area 2 and in between R2 and R4 i'm running OSPF process 3 area 3. Area 1 must be communicated to area 2 and area 3 through OSPF redistribution. how do I configure such network? I have given unique router-id for different processes in router 2

[Peter Paluch · Accepted solution]

Hello,

Unfortunately, what you are trying to accomplish is not possible to my best knowledge.

• You cannot assign a single interface to two distinct areas of a single OSPF instance.
• You cannot run multiple OSPF instances over a single interface.

A possible workaround would be to split the network on f3/0 into multiple VLANs, and create subinterfaces for each of them on f3/0. Then, each subinterface could be put into a separate OSPF area or into an altogether separate OSPF process.

Either way, what is the purpose of this design? Is it just a study assignment, or is this something required in a live network?

Best regards,
Peter

[Mohammed al Baqari]

You don't need redistribution to get this working. R2 will be your ABR
which will allow inter-area routing through type-3 LSA. Once you configure
router ospf with proper areas, things will start working.

[mesghalir]

Another possible solution is "Multi-Area Adjacency Configuration" as explained here: https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/118879-configure-ospf-00.html

here is the sample configuration (single interface in 2 different Areas):

interface Ethernet0/1
 ip address 192.168.23.2 255.255.255.0
 ip ospf network point-to-point
 ip ospf multi-area 99
 ip ospf 1 area 0
 end