Filtering some routes at ABR

[Ali Norouzi]

I  want to configure area 1 as NSSA and I want to filter some routes from  area 0 to 1 at router B. Can I configure router B to advertise default  route + 10.10.10.0/24 to area 1 and filter other routes that are exist  in area0? I don't want to use more than one process-id.

Thank you

[Jon Marshall]

Ali

If you are already advertising a default-route into the NSSA then why do you need to advertise 10.10.10.0/24 ?

The easiest thing would be to configure the NSSA as a totally totally stub NSSA area ie.

router ospf

area 1 nssa no-summary

A totally stub NSSA only has a default route injected into it.

Jon

[Ali Norouzi]

Hi Jon,

I have problem with AToM in this case. The xconnect doesn't come up unless an specific route for LDP router-id exist on the routers in area1. That's why I need to have that /24 route also.

[Mohamed Sobair]

Hi,

If you dont want to make area1 as Totally Stub not so stubby Area, then you can achiev what you are looking for and filter the routes at ABR-B when they are injected into Area 1.

Use the following command at ABR-B:

router ospf x

area 1 filter-list prefix (name) in

ip prefix-list name deny x.x.x.x/x (deny prefixes that you dont want into Area 1)

ip prefix-list name permit 0.0.0.0/0 le 32 (permit all the rest of the prefixes).

HTH

Mohamed

[Ali Norouzi]

Mohammad,

Your solution will filter just LSA type3. Most of my LSAs at area 0 are type5. Is there anyway to filter them?

[Mohamed Sobair]

Hi,

Area 1 is NSSA area, it doesnt accept type-5 LSA, so  you dont need to filter them.

As A general Note, even if Area 1 is not an NSSA , you cant filter type-5 LSA unless you configure the specific Area as stub.

Let me know if this answers your question,

HTH

Mohamed