08-25-2007 12:29 AM - edited 03-05-2019 06:06 PM
hi everyone, i am running ospf with area 0 and area 1. There is an ASBR in area 0 which is injecting 2 routes 40.0.0.0/8 and 30.0.0.0/8. Now i want to advertise only 40.0.0.0/8 in AREA 1. how can i do that ? i tried area 0 filter-list out but it filtered only the IA routes, but in my case i want to filter the specific external routes so how can i do that, i know i have to do something on the ABR in ARea 1 but i dont know how so kindly guide me.
thanks
08-25-2007 01:01 AM
Hi,
This could be accomplished by issuing the command (Area 1 range subnet subnetmask) under the OSPF process of the ABR.
Regards,
Mohamed Sobair
08-25-2007 04:26 AM
Ovais,
There is only two ways you can filter out the external routes.
1) at the ASBR itself.
2) by configuring a stubby or not so stubby area. Note that in this case all external routes will be filtered out from the specific area.
Regards,
08-25-2007 05:21 AM
Hi Hritter,
Yes you are right, I was mistaken of saying command (Area x range) which will filter the summary-routes since the router in area0 is performing ABR/ASBR at the same time.
Apologize guys for misunderstanding the question carfully.
Regards,
08-25-2007 06:26 AM
So wat u mean is that we cannot filter the specific routes on the ABR ?? is there any logic behind it or is it just cisco limitation ???
08-25-2007 10:48 PM
Hi illusion,
As Hritter pointed out, The command (Area x range) where x is the area ID will only summarize the IA (Inter Area Routes), In your case, you can filter external routes using (Route-map) at the ASBR.
For example: you are injecting 10.10.10.0/24 & 10.10.11.0/24 respectively, if you wanna filter the second subnet from being entered the OSPF domain, you just create a route-map when you make redistribution as follows:
route-map (inject-to-ospf)
match ip address 10
Access-list 10 permit 10.10.10.0 0.0.0.255
router ospf 1
redistribute (protocol) route-map (inject-to-ospf)
* With the above you can acheive what you are looking for.
PlS rate if it helps
Regards,
Mohamed Sobair
08-25-2007 11:02 PM
(EDIT)
Dont forget the key word (Subnets) when you make redistribution into OSPF, this will allow OSPF to recognize Classless Subnet.
Regards,
Mohamed Sobair
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