From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Mon Oct 30 2006 - 21:24:08 ART
Ed,
Since OSPF is a link-state routing protocol it is a requirement
that all devices within a link-state area have the same copy of the
link-state database. If one device's database is different than
another's it could result in traffic black holes. For filtering
purposes this implies that you cannot filter a route out of the OSPF
database within an area, but only between areas as the ABR re-originates
them into area 0 or out of area 0. This filtering can occur with stub
areas or the LSA type-3 filter.
Routes cannot be removed from the OSPF database therefore with a
distribute-list, however they can be removed from the routing table. If
you say "distribute-list 1 in" under OSPF you're telling the router to
use access-list 1 to control which prefixes are installed from the OSPF
database into the IP routing table. Be careful with this configuration
as you can end up in traffic black holes if you don't configure an
identical filtering policy on all devices within that link-state area.
HTH,
Brian McGahan, CCIE #8593 (R&S/SP)
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Lab Rat #109385382
> Sent: Monday, October 30, 2006 5:51 PM
> To: cisco@groupstudy.com; ccielab@groupstudy.com
> Subject: OSPF Distribute List Behavior?
>
> Why is my outbound distribute list (distribute-list xx out) not
filtering
> routes as does EIGRP and RIP?
>
>
>
> Is there some inherent OSPF behavior I'm not taking into account?
>
>
>
> Thanks,
>
>
> Ed
>
>
This archive was generated by hypermail 2.1.4 : Wed Nov 01 2006 - 07:29:07 ART