OSPF Areas: The Totally Stubby Area

I just had a break after finishing the Stub Area lab. Yeah, I ate a lot today. One whole chicken chop with Naples’s aglio e olio, crunchy pork knuckle, bitter gourd salad, and banana shake. After a heavy meal, I became drowsy. Then, I sipped 2 cups of Cafe Latte. And, I think I am back. I’m good and I can still count from 1 to 10.

We are back with OSPF areas discussion and this time we will tackle about the Totally Stubby Area. You have to pronounce it right though if you know what I mean.

Totally Stubby Area is a Cisco proprietary feature which works like a Stub Area but a stricter area type. If Stub Area do not allow certain LSA Types like Type 4 and Type 5 LSAs, Totally Stubby area do not allow it as well plus no Type 3 LSA too. The result is even smaller routing table.

To configure Totally Stubby area, we have to add the “no-summary” command after the “stub” command. And, this should be done on the ABR only and not to the routers inside the Totally Stub area. Since my ABR is Anopheles router, I am going to do it here and Aedes stays with my previously configured “stub” command.

Anopheles#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Anopheles(config)#router ospf 2
Anopheles(config-router)#area 20 stub no-summary
Anopheles(config-router)#end
Anopheles#

Anopheles#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Anopheles(config)#router ospf 2
Anopheles(config-router)#area 20 stub
Anopheles(config-router)#end
Anopheles#

On the left is the Stub area result when doing show ip route while on the right is right after we configured it as Totally Stubby area. What did you notice on the routing table? There are no Inter-Area (IA) routes or Type 3 LSA. It converted it with the default route going to the Anopheles router.

Let’s check the difference between a Stub and Totally Stub database:

Totally Stub restricts Type 3 LSA and only allow a default route. The 192.168.1.0, 192.168.2.0, 192.168.12.0 are gone and all that’s left is the default route.

The routing table of Anopheles doesn’t make any difference.

Looking at the database, there is a change like what happened to Aedes router. Of course, they have the same database because they are in the same area.

Let’s check how we can confirm that the area type is Totally Stubby area:

Aedes still showing as a stub area but the Totally Stubby area can be identified on Anopheles. It is showing that it is also a Stub area but there are no-summary LSA which confirms that our area 20 is a Totally Stubby area.