ospf area 0

[brian.kennedy]

Quick question... three areas, call them 0, 100 and 200.  Currently 100 and 200 are both connected only to area 0, with no direct connection between areas 100 and 200.  If a physical link was put in between areas 100 and 200 (creating a start topology between the areas), does 'all' traffic need to go through area 0, thus making the link between 100-200 essentially useless (in terms of traffic routed by ospf), or does just routing updates need to go through area 0?

thanks

[Edison Ortiz · Accepted solution]

All traffic will go via area 0 and the newly created link will be useless.

[JohnTylerPearce]

If you have multiple areas, all inter-area traffic will need to go through Area 0. If you wanted to take a path between Area 100 and Area 200, you would need to configure a loopback interface on that ABR between Area 100 and Area 200, and then assigned that loopback to area 0, since  that lookback will not form an OSPF adjaceny since it is technically not connected to anything that would allow it to receive hellos, it will not form one. But I believe that would allow you to have communicate through Area 100 and Area 200.

But, I agree with Edison, I wouldn't do that personally, but have all areas go through Area 0.