OSPF DISTANCE command, IEWB LAB 13, OSPF task 3.7

From: Herbert Maosa (asawilunda@googlemail.com)
Date: Sat Mar 08 2008 - 07:05:26 ARST

Hi Guys,

I have tried to lab this again and again and my result seem to disagree with
the solution to task 3.7 of IEWB lab 13. So either I may be missing
something very fundamental as the output from the solutions guide shows that
it should work. So hopefully one of you can shed more light on my gaps here.

R1,R2,R6,SW1 ,R3a re originating VLANS 11, 2,6,7 and 367 respectively into
OSPF . R5 has adjacencies with R1 and R2 and recieving these prefixes. The
question is configure R5 such that it prefers the path towards R1 and only
use R2 as a backup.

The solution is to lower the OSPF distance for these routes when they are
learned from R2.

*distance 109 150.1.1.1 0.0.0.0 VIA_R1

*VIA_R1 is a standard access-list that matches the desired routes.
150.1.1.1is the ospf router-id of R1. Now, when I configure this way,
only VLAN 11 (
139.1.0.0/24) has the distance lowered to 109 and R5 prefers this path when
R1 is available. This is what I expect to happen and it is what I am seeing
in the lab, as my understanding is that in the distance command above ,
150.1.1.1 has to be the advertising router-id, and not the next hop from
which you learnt the LSA. So because R1 is only originating VLAN 11, it
seems to work that way, but the other routes are not affected even though
they are learnt from R1 because they are originated form somewhere else.

Now, the show command output from the solutions guide seems to show all
these prefixes with their distance changed to 109, which is suggesting that
the 150.1.1.1 in the distance command would be the router-id of the next-hop
router that you learnt the prefixes from, and not necessarily the
advertising router.

Can someone open my eyes here ? I have tried to find my own asnwer by
labbing this over and over again and I can not reproduce the solution
provided, even if I copy and paste the config from the solutions guide
as-is.

Herbert.

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