Re: OSPF and distribute list

From: Joel A. Cochran (joelc@xxxxxxxxxxxxxxxxx)
Date: Sun Mar 05 2000 - 23:53:49 GMT-3


   
Josh,
    If you were to change your distribute command to read: "distribute-list
7 in Serial1" the route would not appear in downstream routers and you
would not need a distribute list in every router.
    When you use just distribute-list 7 in, it filters the route for that
router only, the route is still advertised. When you add the interface from
which the route is learned, it blocks it from being advertised back out.

Joel Cochran, CCIE# 5448

----- Original Message -----
From: Joshua W. Watkins <josh@mstates.com>
To: <hemi.blandford@equant.com>
Cc: <ccielab@groupstudy.com>
Sent: Sunday, March 05, 2000 4:59 PM
Subject: Re: OSPF and distribute list

Thanks for the tip. I added distribute list 7 in on my ABR and it
stopped the route from coming in. The route that I am trying to
filter however still shows up downstream in routing tables, but can
not be pinged. Check it out.

R8-------R7-------R5

R8#
!
!
!
interface Loopback0
 ip address 10.8.255.1 255.255.255.0
!
!
interface Serial0
 ip address 10.7.240.2 255.255.255.252
 encapsulation ppp
 service-module 56k clock source internal
!
!
router ospf 100
 network 10.8.255.0 0.0.0.255 area 1
 network 10.7.240.0 0.0.0.3 area 1
!

R7#
!
!
interface Loopback0
 ip address 10.7.255.1 255.255.255.0
 no ip directed-broadcast
!
interface Loopback1
 ip address 10.7.253.1 255.255.255.0
 no ip directed-broadcast
!
interface Loopback2
 ip address 10.7.254.1 255.255.255.0
 no ip directed-broadcast
!
interface Loopback3
 ip address 10.7.252.1 255.255.255.0
 no ip directed-broadcast
!
interface Ethernet0
 ip address 10.5.241.3 255.255.255.0
 no ip directed-broadcast
 no keepalive
!
interface Serial0
 ip address 10.6.240.2 255.255.255.252
 no ip directed-broadcast
 no ip mroute-cache
!
interface Serial1
 ip address 10.7.240.1 255.255.255.252
 no ip directed-broadcast
 encapsulation ppp
 ppp authentication chap
!
interface BRI0
 no ip address
 no ip directed-broadcast
 shutdown
 isdn guard-timer 0 on-expiry accept
!
interface Virtual-TokenRing1
 no ip address
 no ip directed-broadcast
 ring-speed 16
!
interface FR-ATM20
 no ip address
 no ip directed-broadcast
 shutdown
!
router ospf 100
 area 1 range 10.7.252.0 255.255.252.0
 network 10.5.241.0 0.0.0.255 area 0
 network 10.7.240.0 0.0.0.3 area 1
 network 10.7.255.0 0.0.0.255 area 1
 distribute-list 7 in
!
!
access-list 7 deny 10.8.255.1
access-list 7 permit any
!

R5#
!
interface Loopback0
 ip address 10.5.255.1 255.255.255.0
!
interface Ethernet0
 ip address 10.5.241.1 255.255.255.0
!
interface Ethernet1
 ip address 10.5.240.1 255.255.255.252
!
interface Serial0
 no ip address
 shutdown
!
interface Serial1
 no ip address
 shutdown
!
router ospf 100
 network 10.5.241.0 0.0.0.255 area 0
 network 10.5.255.0 0.0.0.255 area 0
!

>
>
> Hi
>
> using a distribute-list out to filter outgoing updates dosent work
all that well
> because the LSAs are not considered to be route updates. The only
way to filter
> a route out of a OSPF network is to distribute-list in on every
router for the
> particular route you are filtering. If you "distribute-list in" a
specific
> route, look at the ospf database and you will still see the route
(learned via
> LSA), but the route will not be in the routing table.
>
>
> regards,
> Hemi.
> CCIE# 5585
>
>
>
Joshua W. Watkins
Systems Engineer
Mountain States Networking



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