From: Nick Shah (nshah@xxxxxxxxxxxxxx)
Date: Thu Apr 11 2002 - 02:29:58 GMT-3
Is running an IGP in between these 3 routers an option ??
Nick
----- Original Message -----
From: "Gregg Malcolm" <greggm@sbcglobal.net>
To: <ccielab@groupstudy.com>
Sent: Thursday, April 11, 2002 2:52 PM
Subject: BGP Configuration Question
> This is definitely not a real world question, only to help my
understanding.
> Here's the scenario :
>
> Physical diagram :
>
> R7---serial---R6---serial---R9
> | |
> 60 <---------- 90 <------ Loopback/Token-ring Addresses
>
>
> BGP Neighbor Connectivity and AS #'s
>
> R6---peers---R7---peers---R9
> 65256 79 79
>
> Test is to ping/trace between the 60 and 90 int's. Must use BGP routing
for
> reachabilty between these 3 routers. There are many issues as I see it
with
> this config.
>
> Here are the IP route tables from the 3 routers:
>
> R6
> C 150.20.60.0/24 is directly connected, Loopback60
>
> B 150.20.90.0/24 [20/0] via 150.20.50.7, 01:31:21 <----50.7 is R7
>
> R7
>
> B 150.20.60.0 255.255.255.0 [20/0] via 150.20.50.6, 01:32:52 <---50.6 is
R6
>
> B 150.20.90.0 255.255.255.0 [200/0] via 150.20.69.9, 01:33:10 <---69.9 is
R9
>
> R9
>
> B 150.20.60.0/24 [200/0] via 150.20.50.7, 00:00:09
>
> C 150.20.90.0/24 is directly connected, TokenRing0
>
> I know the logical solution to this problem is to peer across the directly
> connected interface (I.E. R6 should peer with both R7 and R9), but I don't
> want to do that. One of the problems I'm seeing is when I try to ping
from R6
> to R9. R7 sends and ICMP redirect back to R6 saying that R6 know how to
get
> to R9, even tho the route table clearly indicates that the .90 subnet has
the
> correct entries in both R6 and R7. R6 is in fact the path that the packet
must
> take since it has the interface connected to R9. Then of course, R6 sends
the
> packet back to R7 again..classic routing loop. BTW - R7 cannot ping R9
either.
>
> Has anyone else experimented with a config like this (or already knows the
> solution) ? I ran across it accidentally when I was configuring local
pref
> and med.
>
> Thanks, Gregg
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