From: Brian McGahan (brian@xxxxxxxxxxxxxxx)
Date: Thu Jun 20 2002 - 02:24:57 GMT-3
Anthony,
Distribute list can be applied with OSPF, however it cannot be
applied out an interface. Since OSPF is a link state protocol, all
routers within an area must have the same view of the topology. For the
protocol to function correctly, all routers within an area must have the
same routes in the OSPF database.
Distribute list can, however, be applied inbound to an
interface. The reason for this is that you are not filtering the LSA
from coming in the interface. All you are doing is preventing the
prefix from being installed in the routing table. If you check the OSPF
database, the prefix is still there. Since the route is still in the
database, all of the routers still have the same view of the topology.
If a particular router wants to prevent a prefix from being installed
into the IP routing table, that's a different story.
A distribute list may also be applied outbound in general. In
this case, it is only used on an ASBR and in the context of
redistribution. As you can see, the IOS will not allow you to apply a
distribute list out an interface:
router(config-router)#distribute-list 1 out e0
% Interface not allowed with OUT for OSPF
http://www.cisco.com/warp/public/104/9.html#Q9
HTH
Brian McGahan, CCIE #8593
Director of Design and Implementation
brian@cyscoexpert.com
CyscoExpert Corporation
Internetwork Consulting & Training
http://www.cyscoexpert.com
Voice: 847.674.3392
Fax: 847.674.2625
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Anthony Pace
Sent: Wednesday, June 19, 2002 11:46 PM
To: Oliver Boehmer; Volkov, Dmitry (Toronto - BCE)
Cc: ccielab@groupstudy.com
Subject: Re: filtering in OSPF
I have been able to do filtering with a distribute list in OSPF even
though alot of books say it wont work (because the router does not get
"routes" from it's neighbors; it gets lsa's and builds it's own routing
table)
It is intermittent, and I can not figure out why it works for me
sometimes and not others. I tried the IN/OUT distinction discussed in
this thread and it did not seem to be the variable. I think all the
routers had the same IOS.
Is there some other hard and fast distinction of why it would or would
not work?
Anthony Pace
On Mon, 10 Jun 2002 19:13:35 +0200, "Oliver Boehmer"
<oboehmer@cisco.com> said:
> distribute-list in is all there is with OSPF (as with most other RP,
> IIRC,
> only BGP can use route-maps to filter inbound NLRI)..
>
> oli
>
> At 12:48 10.06.2002 -0400, Volkov, Dmitry (Toronto - BCE) wrote:
> >Hi,
> >
> >If there is any way to control - which OSPF routes to install in
routing
> >table based on route tags ?
> >
> >I have loopback 0 and Loop 1 redistributed into OSPF at R1 as
connected . So
> >they are type "O E2" at R2 with tag "1" and "2".
> >I tagged them using route map.
> >Now, I want to install route with tag "1" in routing table at R3 and
not to
> >install route with tag "2"
> >R1--R2--R3
> >
> >Is it possible ? Or distribute list with access list is only way to
do it ?
> >
> >Sincerely,
> >
> >Dmitry
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