From: Reza Toghraee (reza@toghraee.com)
Date: Sat Nov 01 2008 - 13:45:05 ARST
Jason,
R5 is learning prefixes from its iBGP neighbor R1 (i147.10.12.0/24
151.11.15.1 0 100 0 21 21 21 i)
When you issue " neighbor 151.11.100.6 remote-as 67" on R5, then R5 will
learn same prefixes from R6 with AS_PATH Length=2
R5 Advertises these prefixes to R1 (the iBGP neighbor)
R1 will have 2 path to these prefixes, and select the Best path with smaller
AS-PATH which is through R5.
So R1 stops advertising its non_best prefixes to R5, and you will see that
output. But in R1 you must have 2 paths to these prefixes.
Reza
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Jason Morris
Sent: Friday, October 31, 2008 6:11 AM
To: Cisco certification
Subject: Silly BGP question
can anyone tell me why these prefixes aren't showing up multiple time, once
for each path. it looks like when i'm learning them from the ebgp peer that
i config in the output the prefixes aren't showing up in the table from the
ibgp peer i'm learning them from as well. output is below, sorry if the
question is to vague or doesn't make sence... not sure how else to ask it.
R5(config-router)#do sho ip bgp
BGP table version is 73, local router ID is 151.11.5.5
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i147.10.12.0/24 151.11.15.1 0 100 0 21 21 21 i
*>i147.10.13.0/24 151.11.15.1 0 100 0 21 21 21 i
*>i147.10.14.0/24 151.11.15.1 0 100 0 21 21 21 i
*>i147.10.15.0/24 151.11.15.1 0 100 0 21 21 21 i
*>i192.168.0.0 151.11.15.1 0 100 0 21 21 21 i
*>i192.168.1.0 151.11.15.1 0 100 0 21 21 21 i
*>i192.168.2.0 151.11.15.1 0 100 0 21 21 21 i
*>i192.168.3.0 151.11.15.1 0 100 0 21 21 21 i
R5(config-router)#neighbor 151.11.100.6 remote-as 67
R5(config-router)#
*Oct 31 03:16:43.990: %BGP-5-ADJCHANGE: neighbor 151.11.100.6 Up
R5(config-router)#do sho ip bgp
BGP table version is 81, local router ID is 151.11.5.5
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 147.10.12.0/24 151.11.100.6 0 67 21 i
*> 147.10.13.0/24 151.11.100.6 0 67 21 i
*> 147.10.14.0/24 151.11.100.6 0 67 21 i
*> 147.10.15.0/24 151.11.100.6 0 67 21 i
*> 192.168.0.0 151.11.100.6 0 67 21 i
*> 192.168.1.0 151.11.100.6 0 67 21 i
*> 192.168.2.0 151.11.100.6 0 67 21 i
*> 192.168.3.0 151.11.100.6 0 67 21 i
R5(config-router)#
Jason
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