LOCAL_PREF example in Doyle, Routing TCP/IP Volume II page 242

From: Xuan.Sun@xxxxxxxxxxx
Date: Mon Aug 27 2001 - 00:13:30 GMT-3

   
Hi All

I have posted a message talking about LOCAL_PREF before. I hit this problem
again when I tried the example on Dolye's book.

The diagram and configuration are at Page 242-243. Dolye uses this example
to manipulate the LOCAL_PREFERENCE. So it will take the route to AS 50
using Innsbruck, AS 75 using Saalbach.

On Zermatt, there are two paths to reach AS 75, for example the route
172.18.0.0. It either takes Innsbruck or Moritz. The Innsbruck is the EBGP
peer. Moritz is the IBGP peer. Because the Innsbruck is the EBGP peer. BGP
always uses it as the next hop.

Dolye assigns a high Local_Pref number (300) on Moritz. It send to Zermatt.
So on Zermatt, the next hop to 172.18.0.0 from Moritz increased to 300,
instead of the default 100. So BGP will take Moritz as the next hop for
172.18.0.0. The "show ip BGP" is on Page 244.

I have built up the same network and configuration. But it does not work in
the way as Dolye's. I can see the Locale_Pref has been changed to 300. But
BGP still takes Innsbruck. See my "show ip bgp" on Zermatt. I have aligned
the output. But it may not display on your machine.

Have somebody tested this configuration before ? Did you have the same
problem ? Is it a IOS bug ? I am using 3810, IOS 12.0.(7)T for Moritz and
Zermatt.

Your feedback is highly appeciated. I am tied to this Locale_Pref
attribute.

Zermatt#sh ip bgp
BGP table version is 23, local router ID is 172.30.255.254
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network Next Hop Metric LocPrf Weight Path
* i10.20.0.0/16 172.30.255.150 100 0 100 50 ?
*> 10.100.83.1 200 0 100
 50 ?
* i10.30.0.0/16 172.30.255.150 0 100 0 ?
*> 192.168.3.3 0 32768 ?
* i10.50.250.1/32 172.30.255.150 100 0 100
 50 ?
*> 10.100.83.1 200 0 100
 50 ?
* i10.75.100.1/32 172.30.255.150 100 0 100 50 ?
*> 10.100.83.1 200 0 100
 50 ?
*> 10.100.65.1/32 10.100.83.1 200 0 100 50 ?
*>i10.100.83.1/32 172.30.255.150 100 0 100
 50 ?
* i172.16.0.0 172.30.255.150 0 100 0 ?
*> 192.168.3.3 0 32768 ?
* i172.17.0.0 172.30.255.150 100 0 100
 50 ?
*> 10.100.83.1 200 0 100
 50 ?
* i172.18.0.0 172.30.255.150 300 0 100 75 i
*> 10.100.83.1 0 100
 75 i
* i172.29.1.0/24 172.30.255.150 0 100 0 ?
*> 192.168.3.3 0 32768 ?
* i172.29.2.0/24 172.30.255.150 100 0 100
 50 ?
*> 10.100.83.1 200 0 100
 50 ?
*> 172.30.255.150/32
                              192.168.3.2 0 32768 ?
* i172.31.0.0 172.30.255.150 0 100 0 ?
*> 192.168.3.3 0 32768 ?
* i192.168.50.0 172.30.255.150 100 0 100
 50 ?
*> 10.100.83.1 200 0 100
 50 ?
* i192.168.100.0 172.30.255.150 0 100 0 ?
*> 192.168.3.3 0 32768 ?
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