OSPF question

[Bruce123]

Hi,

 

I just have a quick question regarding OSPF and advertising networks, that I hope someone could assist with?

 

There are 2x layer 3 switches (OSPF routers) connected together via a link (all in the same OSPF area including the link itself).

 

Obviously, the link (IP) network exists on both layer 3 switches. Which layer 3 switch should advertise the network, one or the other or both?

 

The backgroud to this is that under the proposal we have 3 switches; Switch1 has several IP Networks/VLANs defined (the core for the site) which are advertised into OSPF area 10. The link to Switch2 is using a network already defined on Switch1 (10.0.0.0/24) and is used for various hosts. Switch2 connects to Switch3 (at another site) as area 0.

 

So, my question is, should the network 10.0.0.0/24 be advertised as area 10 by Switch1 or Switch2 or both? If Switch1, then it would leave Switch2 not advertising any networks at all (other than into area 0), leaving no actual management IP address for the switch.

 

[switch2]---area 0---[switch3]

|10.0.0.254

|

| area 10

|

|10.0.0.1

[switch1]

 

I hope that makes sense?

 

Thanks,

 

Bruce.

Edited June 23, 2020 by Bruce123

[stevec_]

You would need to advertise the 10.0.0.0/24 network on Switch1 and Switch2 so that they would form an adjacency. Edited June 23, 2020 by stevec_

[Bruce123]

You would need to advertise the 10.0.0.0/24 network on Switch1 and Switch2 so that they would form an adjacency.

 

Can they not form an adjacency without advertising the ‘link’ network? I.e. As long as OSPF is enabled on the

ports they will learn about each other using multicasts?