From: Shine Joseph (shinepjoseph@iprimus.com.au)
Date: Thu Mar 13 2008 - 07:46:19 ARST
Emil,
The fact that origin code is ahead of MED in best path calculation, you can
change the origin code to accomplish this task.
If there is no restriction in how you advertise the networks in AS123, I can
think of advertising the network with origin code of igp to R4 from R1. If
you are restricted with no-redistribution, then apply a route-map in the
network statement to change the origin code to incomplete.
I have labbed up your scenario and it works.
HTH,
Shine
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
YourPal
Sent: Thursday, 13 March 2008 5:19 PM
To: Cisco certification
Subject: Question on Influencing BGP Inbound Path Selection
Hi Group,
I came across the following BGP scenario:
R1, R2, and R3 are in AS 123. They are fully-meshed. R4 is in AS 456. R4
peers with R1 and R2.
R1 advertises 172.16.1.1/32 into BGP.
R2 advertises 172.16.2.2/32 into BGP.
R3 advertises 172.16.3.3/32 into BGP.
Configure R1 so that R4 prefers R1 to reach 172.16.1.1/32 and 172.16.3.3/32.
Route filtering and AS path manipulation are prohibited.
The way I see it, I'm left with the option of configuring MED. However since
the task restricts the config to be done on only R1, AFAIK there's no way to
influence MED because both R1 and R2 will advertise the prefixes to R4 with
MED=0 (unless I'm allowed to configure a higher MED value on R2).
Can't think of a solution. I may be missing something. Appreciate any help.
Thank you.
BR,
Emil
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