From: Serhat Aslan (serhatworks@gmail.com)
Date: Fri Jul 20 2007 - 19:59:40 ART
Hi Ben
Distribute-list effect the routing table. Distance vector protocols send
their best routes(routing table routes)to each other. But linkstate protocol
use database instead of the routing table. Linkstate protocol process the
database to take the best routes, The distribute-list can not directly
effect the database so whenever the database synchronization will be, the
other routers take the database and produce unwanted routes.
at the solution 1 probably it effect not to enter the routing table, not
to effect the database sync. within the AREA. AFAIK, this commands
effectively worked at outbound for ASBR redistributed routes.
----
Serhat Aslan
On 7/21/07, Ben <bmunyao@gmail.com> wrote:
>
> Hi
>
> This is a scenario I encountered in an IE lab. IGP is OSPF and the
> requirement is to have R1 get the 10.10.4.0/24 subnet from only one
> source.
>
> 10.10.1.0/24
> /-------------R2----|
> / |
> R1------/ |10.10.4.0/24
> s0/0 \ |
> \ |
> \--------------R3---|
>
>
> R1 gets the route 10.10.4.0/24 from R2 and R3 thro OSPF
>
> O 10.10.4.0 [110/65] via 10.10.1.2 .......
> [110/65] via 10.10.1.3 ........
>
> In order to filter out the advert from R3 and use only R2 for forwarding,
> one can use an extended ACL as follows:
>
> Solution 1
>
> access-l 100 deny host 10.10.1.3 host 10.10.4.0
>
> router ospf 1
> distribute-list 100 in s0/0
>
> I tried using a route-map to do the same without much success. Here is
> what
> i did:
>
> Solution 2
>
> ip pref vl4 permit 10.10.4.0/24
> ip pref R3 permit 10.10.1.3/32
>
> route-m FILTER deny 10
> match ip add pref vl4
> match ip next-hop pref R3
> route-m FILTER permit 20
>
> router ospf 1
> distribute-list route-m FILTER in
>
> Solution 3
>
> p pref vl4 permit 10.10.4.0/24
> ip pref R3 permit 10.10.1.3/32
>
> route-m FILTER deny 10
> match ip add pref vl4
> match ip route-source pref R3
> route-m FILTER permit 20
>
> router ospf 1
> distribute-list route-m FILTER in
>
>
> Neither solution 2 nor solution 3 worked for me. Logically they appear
> sound. i would appreciate any comments on these approaches.
>
> TIA
> Ben
>
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