OSPF Network Question

[cadams]

I have two routers, both are ABR's Area 0 is defined as:

network 172.16.1.0 0.0.0.255 area 0

network 172.16.2.0 0.0.0.255 area 0

I then want to route networks 172.16.5.0 and 172.16.6.0 in another area such as area 1. What adverse affects would happen if I did the following:

network 172.16.1.0 0.0.0.255 area 0

network 172.16.2.0 0.0.0.255 area 0

network 172.16.0.0 0.0.255.255 area 1

The network statement for area 1 overlaps with area 0. Will this cause any problems?

[steve.barlow]

In OSPF network statement order matters. The first statements will place the specific 172.16.x.0 networks in area 0, then it will read the third line and put the rest of the 172.16.0.0 in area 1. It will work.

It wouldn't work if you placed the general 172.16.0.0 before the 172.16.1.0 command - they would all be in area 1.

Hope it helps.

Steve

[cadams]

Even though you say this will work shouldn't it be done so that the route is more specific?

Thanks for your help.

[steve.barlow · Accepted solution]

Yes, I believe it should always be as specific as possible. Minimizes chance of error. However, having said that, being general and broad may save you time in configuring and config space if you know all your interfaces will be in a given area. It depends on the situation.

Steve

[cadams]

Thank you so much for your help Stever.