ospf route filtering

Unanswered Question
Jul 24th, 2008
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Hi dudes,

I need to achieve outboud route filtering on ABR.

ABR has got 2 area 0 and area 50, it is receiving external type 1 routes from area 50, I would like to inject some of these routes into ospf area 0 and filter all other routes.


I tried with distribute-list and it's not filtering and area 0 routers learning all the routes from ABR.


Cheers,


Rajesh

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lee.reade Thu, 07/24/2008 - 03:37
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Hi,


In order to filter your type 5 E1 routes you will need to perform the filtering on the ASBR and not the ABR.


HTH


LR

rajeshk200_2 Thu, 07/24/2008 - 03:57
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Hi

thanks for response

ASBR has got only one area 50(planning to have multiple area later stage ) and it is injecting all static routes in to ospf process, I need to inject only specfic routes injected into ospf ABR which is having area 0 and 50.


in the expansion process lot more ABR coming and need to receive specific static routes from ASBR, that's reason I am redistribuiting all the static routes into ASBR OSPF process.


How do I achieve required routing for this.


Cheers,


Rajesh

lee.reade Thu, 07/24/2008 - 04:25
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Hi,


The only way you can filter the external routes, if not on the ASBR is on the actual router itself, ie distribute list in, this will prevent the route from showing in the routing table but does not filter it from within the ospf database.


HTH


LR

rajeshk200_2 Thu, 07/24/2008 - 06:02
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Hi,

I have done exactly the same, As you said I can see only permitted routes in ABR routing table but not on area 0 internal router, seemingly learning all routes fom ABR's ospf database and distribute-list out has no effect on routing filtering.


Is there any other remedy to filter type 5 lsa based on IP prefix on ABR?


Cheers,

Rajesh

Kevin Dorrell Thu, 07/24/2008 - 06:47
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Here is a long shot, and I don't know whether it would work 'cos I have not tried it.


Try putting in an area range summary that corresponds to the route(s) you are trying to filter out. Does that make it a type 3? If so, try adding an area filter to filter it out. (Normally an area filter will filter type-3s but not type-5s.)


It's a whacky idea, so I have no idea whether it would work.


http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp1.html#wp1011537

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp1.html#wp1011184


Kevin Dorrell

Luxembourg


rajeshk200_2 Fri, 07/25/2008 - 01:21
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Kevin,


I tried that and it has no effect on route filtering.


I am scratching my head to find any alternative and any help would be appreciated.


Cheers,

Rajesh



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