OSPF behavior

[beckerola]

Hi

I have a little doubt. Does OSPF still propagates even if the interface that has the network is down?

I'm doing a migration from one 7500 to another and a few point to point links will be changed. The configuration is the same less the IP tu manage the Router.

I`m not sure if it would be right to turn on the new 7500 with all the OSPF config already made. The interfaces are administrativily down, and i think it will not harm anything, but not sure though...

Thanks

[pkhatri]

The short answer is: no... By default, OSPF will only propagate routes (or I should say the networks) for interfaces that it is enabled on and that are administratively and operationally up (i.e. the interfaces have to be in a up/up state).

So you should be okay to do what you are suggesting...

Hope that helps - pls do rate the post if it does.

Paresh

[beckerola]

Thanks, that was very helpful

[beckerola]

Hi

Having a final look to my configuration in the 7500, I found that although all the interfaces are down and OSPF will not be a problem activating the router, there's a Loopback interface which is the ID and identifies the router in the OSPF environment.

The network command only announces the interface like the following; "network 192.168.x.x 0.0.0.0 area 0"

The ID will be certainly propagated and therefore a change will occur in OSPF, so maybe a should turn on the router by night in a window hour.

Is this correct?

Thanks

[pkhatri]

Does the "network 192.168.x.x 0.0.0.0 area 0" cover the loopback interface ? If it does not, OSPF will NOT advertise it as a route even if it uses it as the rotuer ID. You can always force OSPF to use a specific address as the router ID by using the "router-id" command under the "router ospf" configuration.

In any case, it is always sensible to make such changes during an outage window.

Hope that helps - pls do rate the post if it does.

Paresh

[beckerola]

Yes, it does. We propagate the 192.168.0.0/24 for this specific use. Anyway, I already prepared the migration for one of these nights. Don't want anything strange happening, plus being me doing the job :)

Thanks Paresh

[jbrunner007]

dont forget if you want to advertise a /24 loopback, you need ospf network point-to-point otherwise, by default its a /32 advertisement for the loopback, regardless of assigned mask.

Joe