Can a interface join two OSPF processes?

[caobo1020]

I was trying to understand what would happen if I put an interface into two OSPF processes. It seems only one process will learn the route and send it to its peer. Can anyone verify and explain this?

e.g config:

router ospf 100

network 10.1.1.0 0.0.0.255 area 0

network 192.168.1.0 0.0.0.255 area 0

router ospf 2999

network 10.1.1.0 0.0.0.255 area 0

network 172.16.10.0 0.0.0.255 area 0

Thanks,

Bo

[Gabriel Hill · Accepted solution]

Hello Cao,

You're correct, Each interface can only be a part of one OSPF processes. So whichever process is the first to initialize will be the one to "claim" that interface. If that processes goes down the next processes in line would take over that interface.

[caobo1020]

Thank you for the answer Gabriel.

[Nagendra Kumar Nainar]

Hi Cao,

The idea of having one interface part of different area is documented in RFC5185. I beleive this is spported in XR but not yet in IOS.

Thansk,

Nagendra

[Giuseppe Larosa]

Hello Bo,

the root cause is that OSPFv2 does not carry the OSPF process id into the OSPF packets so it cannot discriminate betweeen packets of different processes if the OSPF area is the same.

The OSPF area-id is carried in OSPFv2 packets, so running two different OSPF processes in two different OSPF areas on the same L3 interface should be supported also in IOS.

In OSPFv3 things are different as the OSPF process-id is carried within the packets and/or there is an instance concept.

Hope to help

Giuseppe