RE: [nsp] how to fool the SPF in OSPF?

From: Chris Davis (chris.davis@computerjobs.com)
Date: Mon Jun 11 2001 - 16:04:32 EDT


The order of preference for OSPF routes are as follows:

intra-area routes, O
inter-area routes O IA
external routes type 1, O E1
external routes type 2, O E2

I'm not completely sure about your areas, but it looks like you want traffic
from routerB to traverse area1 to routerA in area 0.

If the T1s could be in area 1 rather than area 0, as they probably should be
based on bandwidth, your problem should be solved.

-----Original Message-----
From: jlewis@lewis.org [mailto:jlewis@lewis.org]
Sent: Monday, June 11, 2001 3:46 PM
To: cisco-nsp@puck.nether.net
Subject: [nsp] how to fool the SPF in OSPF?

Given a network such as:

-----------------------------------
| routerA------T3------routerC |
|___ | _________________ | __| area 0
   | | | | | |
   | T1s | | T3 |
   | | / | | |
    \ | / /-------------\ \ | /
    routerB-----100bt------routerD
           \-------------/
                area 1

how do I get around the T1's connecting A and B being the shortest path
and get B to send traffic to A via D unless one of the T3's above is down?
I can't just use static routes on B, because it won't know if a T3 is
down. I've tried playing with "ip ospf cost" on the T1's but B still
prefers them.

-- 
----------------------------------------------------------------------
 Jon Lewis *jlewis@lewis.org*|  I route
 System Administrator        |  therefore you are
 Atlantic Net                |
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