OSPF adjancency on secondary network

[J1mbo78]

Hi,

Does anybody know a trick for getting an OSPF adjancency to form on a secondary network?

I have an ethernet interface with a secondary ip address - I want the adjancency to form with a neighbour that is addressed from the secondary subnet.

Many Thanks,

James

 

[lui3]

post your configuration.

you can also use the a loopback address in the neighbor statement if you are looking at the router id.

 

[baddos]

Shouldn't be a problem since OSPF uses multicasts and not unicast packets. So the secondary address subnet should receive those packets.

However, you'll need to be sure that you are advertising both of those networks in your OSPF config.

 

[J1mbo78]

Hi,

We tried everything to no avail and then I found this in the Cisco Press Routing TCP/IP Volume 1 by Jeff Doyle (a brilliant reference book by the way):

"OSPF sees secondary networks as stub networks (networks on which there are no OSPF neighbours) and therefore will not send Hellos on them. Consequently, no adjacencies can be established on secondary networks."

Oh well. By the way, it was a pix firewall so we couldn't use loopbacks, we had to re-address it in the end.

Cheers,

James

 

[baddos]

Sorry to hear the bad news.

It's not good practice to use secondary networks in a live environment anyways though. It makes the hole thing too confusing and will waste bandwidth on that interface.