ospf - stub area

[Antelope]

I want to classify one of my subnets as a stub area in OSPF (because it will only communicate with the adj network) but I cannot get the two areas to exchange routes. What am I missing in my config:

Router A would be the Stub area

RouterA
fa0/0
ip address 10.1.10.1 255.255.255.0

s0/0
ip address 192.168.1.2 255.255.255.0

router ospf 1
network 10.1.10.0 0.0.0.255 area 1


Router B
fa0/0
ip address 172.16.1.1 255.255.0.0

s0/0
ip address 192.168.1.1 255.255.255.0

ospf 1
network 172.16.0.0 0.0.255.255 area 0

 

[BuckWeet]

on router A do this


router ospf 1
network 192.168.1.0 0.0.0.255 area 0
area 1 stub

router B do this

router ospf 1
network 192.168.1.0 0.0.0.255 area 0



BuckWeet

 

[Cluebird]

BuckWeet has it right. Just make sure any other routers in Area 1 also have the area 1 stub command. And since you're stubbing the area, why not go totally stubby and add on Router A "area 1 stub no summary

 

[Antelope]

Thanks for your help, just for clarification on my part:


So a stub network will not see external routes, and always must use the default route for that network to get out, while a Totally Stubby area is the same thing, only Cisco proprietary?

 

[lambent]

I can only say that totally stubby area is not mentioned in the original OSPF v2 RFC but actually it's just a stub area without inter-area routes (summary routes) being propagated inside. Even other vendors such as Nortel have similar implementation of a "totally stubby area" but they may not be using the same name.

On the other hand, Not-so-stubby-area is an open standard (RFC 1587).

 

[Cluebird]

When you stub an area, the default route is used for the internal routers to get out. That eliminates the summary LSAs. The totally-stubby removes all but Type 1 and Type 2 LSAs which saves some bandwidth. The only router that needs to be Cisco for a totally-stubby is the ABR.

The NSSA implementation requires all routers in the area have the "area 1 nssa" instead of the "area 1 stub". Cisco tweaks this with "area 1 nssa no-summary" to create a totally-stubby not-so-stubby area on the ABR. The main difference between stub and nssa is you can attach an ASBR to a nssa and inject routes from another routing process (EIGRP, RIPv2, etc.). Those routes use a Type 7 LSA which propagates across the NSSA and get changed to Type 5 LSAs by the ABR (which actually is also the ASBR).