OSPF - CBT CCNP VID 22 - Config

Question 1

How to configure stub area ?

Answer 1

all routers in the area have to have the stub in their config or it won’t form neighbor relationship

> router ospf 1
area 23 stub

Routers only inside the ‘Stub Area’ - after this command is entered all External routes (E1,E2) will be removed from the routing table.

The ABR Routers is in charge of default routing to the external destination.
When the ABR is configured for ‘Stub area’ it automatically creates a default route for all routers in that ‘stub area’ to reach the External routes.
The ABR will be the only router connected to the ‘Stub area’ that still has external router (E1,E2) in it routing table.

Question 2

How to configure Totally stub area ?

Answer 2

The config below should go on the ABR router only

> router ospf 1
area 45 stub NO-summary

But all the routers within this ‘totally stubby area needs to have the config that is the same as ‘stub area’ it doesn’t need the ‘No-summary’ part as this is done by the Cisco router as it is cisco proprietary protocol part.

> router ospf 1
area 45 stub

Automatically the default route will be generated by the ‘totally stubby config’