HI BVS, [Pls Rate if HELPS]

In addition to Kevin's POST.

OSPF has special restrictions when multiple areas are involved. If more than one area is configured, one of these areas has to be Area 0. This is called backbone. When designing networks it is good practise to start with Area 0 and then expand into other areas later on.

The Backbone has to be center for all other areas ie., all areas have to be physically connected to Backbone. The reason behind that is that OSPF expects all areas to inject routing information into the backbone and in turn the backbone will disseminate that information into other areas.

To just startup & run with only as "Single Area OSPF", any Area can be defined with any process id.

Hope I am Informative.

Pls RATE if HELPS

Best Regards,

Guru Prasad R

Points to u.

Dude, consider a scenario where four of my interfaces on a router are each in separate area. But they all talk to each other without any backbone configured. If a backbone (area0)is req for inter-area communication, how does the above communication take place.

There are two ways this could work:

1. There is a default route being advertised into all the areas from the one router connected to all of them. This would draw all the interarea traffic to the one router in the network with full routing knowledge.

2. http://www.ietf.org/rfc/rfc3509.txt

Other than one of these two being true, it shouldn't work.

:-)

Russ

This works because if you take OSPF off, you should still get between interfaces. They are connected interfaces in the routing table, not OSPF routes.

Your going to be able to route between interfaces because that's what a router does.