08-22-2008 05:13 AM - edited 03-03-2019 11:14 PM
Hi,
Here's the situation â¦. I have a remote router acting as an ABR for both OSPF area 5 and area 0. In area 5, I have a network address of 10.1.2.0 /24 that I want to keep advertising in area 5 but not to have the network advertised via area 0. The reason for this is the network is a conflict that can't be removed at this time.
What's easier, to try to filter on this specific router or to filter on the far end router, that is a backbone router. Any suggestions? i.e route map vs. distribute list vs. pre-fix list?? I would appreciate a sample config as to how this could be done.
Thanks,
Steve
Solved! Go to Solution.
08-22-2008 05:38 AM
All will depends on the type of route this network appears as and the types of areas you are using.
In the best case if it appears as a type 3 . Then you can use prefix lists to filter on area. When the routes appear as externals or intra area routes your options are very limited.
http://www.cisco.com/en/US/docs/ios/12_2t/12_2t11/feature/guide/ft11at3f.html
08-22-2008 06:00 AM
Hello Steve,
have the net 10.1.2.0/24 advertised in area 5.
At the ABR(5,0) you can filter it by using an area filter-list.
http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp1.html#wp1011184
or area 5 range 10.1.2.0 255.255.255.0 not-advertise under router ospf process on ABR(0,5).
http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp1.html#wp1011537
Avoid to have this subnet redistributed into OSPF because LSA type 5 cannot be filtered out of the OSPF database.
Hope to help
Giuseppe
08-22-2008 05:38 AM
All will depends on the type of route this network appears as and the types of areas you are using.
In the best case if it appears as a type 3 . Then you can use prefix lists to filter on area. When the routes appear as externals or intra area routes your options are very limited.
http://www.cisco.com/en/US/docs/ios/12_2t/12_2t11/feature/guide/ft11at3f.html
08-22-2008 06:00 AM
Thanks, interesting way to handle this. The newtork actually originates on a VLAN on the ABR (it's a L3 switch) so based on the link, I should be able to filter in area 5 outbound to prevent area 0 from seeing the network.
Appreciate the quick response.
Cheers,
Steve
08-22-2008 06:00 AM
Hello Steve,
have the net 10.1.2.0/24 advertised in area 5.
At the ABR(5,0) you can filter it by using an area filter-list.
http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp1.html#wp1011184
or area 5 range 10.1.2.0 255.255.255.0 not-advertise under router ospf process on ABR(0,5).
http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp1.html#wp1011537
Avoid to have this subnet redistributed into OSPF because LSA type 5 cannot be filtered out of the OSPF database.
Hope to help
Giuseppe
08-22-2008 06:24 AM
Thanks, appreciate the feedback Giuseppe.
Steve
08-22-2008 09:27 AM
Hi,
I did a lab test and it worked perfect - exactly as I need.
Thanks to both of you for your help.
Steve
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