From: Bob Sinclair (bsin@xxxxxxxxx)
Date: Wed Mar 06 2002 - 16:15:37 GMT-3
Just a thought: what if you raised the admin distance for ospf routes learned
from the router on the other side of the BRI? I have had some success doing th
is with ospf.
----- Original Message -----
From: "Paul Borghese" <paul98@prodigy.net>
To: <ccielab@groupstudy.com>
Sent: Wednesday, March 06, 2002 1:34 PM
Subject: Virtual Links and Backup Interfaces in OSPF
> Hi,
>
> I have created a practice scenario using the following setup (OSPF protocol):
>
> R1 is connected to R2 and the connection is in Area 0. R2 is connected to R5
> in Area 100. R5 has a backup ISDN link to R1. I made this backup Link area
> 101 and created a virtual link through area 101 to connect Area 100 in case
> the connection to R2 ever went down. R1 has a route (172.16.1.0) which is in
> Area 0.
>
> The problem I am having is R5 always prefers to use the BRI interface to get
> to 172.16.1.0 instead of using the connection to R2. I even set the cost of
> the BRI interface to be 10x that of the R2 connection. Here is the results o
n
> R5:
>
> With the ISDN line active:
> 172.16.0.0/24 is subnetted, 1 subnets
> O 172.16.1.0 [110/10010] via 190.27.1.66, 00:52:04, Dialer0
>
> With the ISDN in Shutdown mode:
> 172.16.0.0/24 is subnetted, 1 subnets
> O IA 172.16.1.0 [110/943] via 190.27.1.33, 00:00:03, Serial4
>
> Notice with the ISDN active, the router prefers to use the Dialer interface
> even though the metric is 10010 versus the Serial 4 interface with a metric o
f
> 943! I believe this is because the route learned via the Dialer0 interface i
s
> an interior route and the route learned via the S4 interface is an InterArea
> route.
>
> So is there any way to get R5 to prefer the S4 route with the Dialer interfac
e
> active? Of course one way to fix this would be to make the ISDN line area
> 100 and dump the Virtual Link. But I am wondering if there is a way to do it
> using the typology I created.
>
> Paul Borghese
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