OSPF Stub Areas Allow type 4 (ASBR Summary) LSA or not

[s-ralli]

Some texts show that type 4 lsa is allowed inside a stub area ? is it tru ..?

The ABR sends a type 3 default route into the area by default (Whether it has a default route itself or not)

Regarding the totally stub area , no type 3,4,5 are allowed and only a type 3 default route is sent by the ABR into the area...

My 2nd Q is

regarding the NSSA areas, the ABR will not send a default route unless it is configured with

area # nssa default-information-originate

so in this case the ASBR (Router with area # nssa default-information-originate configured will send a default route (Type7) into the area but does the default route need to exist in the ASBR RT ? is it mandatory to include "always" with default-information-originate so that the ASBR sends the default route into the NSSA without cheking its own RT for the default route ?

Thanks

[Harold Ritter]

1. Type 4 LSAs are not propagated in stubby areas. They wouldn't be of any use since no external lsas are present in such areas.

2. The NSSA ABR doesn't need a default route in it's routing table to generate a type 7 default route in the the NSSA area when "area x nssa default-information-originate" is configured. The always keyword is not available for that command.

Hope this helps,

[Kevin Dorrell]

Harold,

I'm glad you answered this question. I checked in the CCIE flash Cards set (page 64 of the PDF version) - and didn't get the answer I was expecting. So I've been puzzling over it all afternoon. I couldn't think why the stub area would want to know how to get to the ASBR if there were no type 5s in the area. But I guess it was a misprint in the flash cards.

Kevin Dorrell

Luxembourg