GoBucks82 Thu, 12/27/2007 - 16:09

The OSPF process ID is locally significant to each router. OSPF does not check the process ID when adjacencies are formed between neighboring routers and routing information is exchanged.

The only case in which the OSPF process number is taken into account is when OSPF is used as the routing protocol on a Provider Edge to Customer Edge (PE-CE) link in a Multiprotocol Label Switching (MPLS) VPN. PE routers mark OSPF routes with the domain attribute derived from the OSPF process number to indicate whether the route originated within the same OSPF domain or from outside it. If the OSPF process numbering is inconsistent on PE routers in the MPLS VPN, the domain-id OSPF mode command should be used to mark that the OSPF processes with different numbers belong to the same OSPF domain.

Hope that helps.

swmorris Fri, 12/28/2007 - 19:51

The short answer is whenever you want to keep sets of routes separated between different sets of peers.

While area-based filtering gives you some controls, depending on what details we're talking about that can become difficult if not impossible.

Running completely separate processes of OSPF (or whatever routing protocol) gives you more control as the databases are completely different.



[email protected]


This Discussion