From: Narbik Kocharians (narbikk@gmail.com)
Date: Wed Sep 12 2007 - 13:38:39 ART
This can happen if you are establishing an E/IBGP using the loopback
interfaces that are advertised in BGP. I can't see all the configs
On 9/12/07, cciehksg <cciehksg@yahoo.com.sg> wrote:
>
> Hi there
>
>
>
> when building pure ibgp-ebgp network as below :
> routes in R1 show up in R4's BGP table, but not in R4's routing table ?
> but sometime the R1's route appear in R4's routing table for a while
>
> and if we observe the bgp table, sometime the route shows as best(>)
> and then the best status dissappeared
> i also noticed that the bgp table version number keep incrementing
>
>
> R1-------------------------------------R2----------------------------------------------R3-------------------------------------------R4
> -
> 10.10.10.1 /8 __ 10.10.10.2 /8 __ 172.172.172.2 /16 __ 172.172.172.3 /16
> __192.168.1.3 /24 __ 192.168.1.4 /24
>
>
> R1 in AS 100
> R2,R3,R4 in AS 200
>
>
> R1
> router bgp 100
> nei 10.10.10.2 remote-as 200
> net 10.0.0.0
> no auto-summary
>
> R2
> router bgp 200
> no sync
> nei 10.10.10.1 remote-as 100
> nei 172.172.172.3 remote-as 200
> nei 192.168.1.4 remote-as 200
> net 10.0.0.0
> net 172.172.0.0
> no auto-summary
>
> R3
> router bgp 200
> no sync
> nei 172.172.172.2 remote-as 200
> nei 192.168.1.4 remote-as 200
> net 172.172.0.0
> net 192.168.1.0
> no auto-summary
> R4
> router bgp 200
> no sync
> nei 172.172.172.2 remote-as 200
> nei 192.168.1.3 remote-as 200
> net 192.168.1.0
> no auto-summary
>
> R4#sh ip bgp
> BGP table version is 29, local router ID is 192.168.1.4
> 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
> *>i10.0.0.0 172.172.172.2 0 100 0 i
> *>i172.172.0.0 172.172.172.2 0 100 0 i
> * i 192.168.1.3 0 100 0 i
> * i192.168.1.0 192.168.1.3 0 100 0 i
> *> 0.0.0.0 0 32768 i
>
>
> R4#sh ip ro
> Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
> i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
> ia - IS-IS inter area, * - candidate default, U - per-user static route
> o - ODR, P - periodic downloaded static route
> Gateway of last resort is not set
> B 172.172.0.0/16 [200/0] via 172.172.172.2, 00:00:56
> B 10.0.0.0/8 [200/0] via 172.172.172.2, 00:00:56
> C 192.168.1.0/24 is directly connected, Serial0/0
>
> R4#sh ip bgp
> BGP table version is 31, local router ID is 192.168.1.4
> 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
> * i10.0.0.0 172.172.172.2 0 100 0 i
> * i172.172.0.0 172.172.172.2 0 100 0 i
> *>i 192.168.1.3 0 100 0 i
> * i192.168.1.0 192.168.1.3 0 100 0 i
> *> 0.0.0.0 0 32768 i
>
> this is when the routes in R1 disappeared
>
>
> R4#sh ip ro
> Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
> i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
> ia - IS-IS inter area, * - candidate default, U - per-user static route
> o - ODR, P - periodic downloaded static route
> Gateway of last resort is not set
> B 172.172.0.0/16 [200/0] via 192.168.1.3, 00:00:16
> C 192.168.1.0/24 is directly connected, Serial0/0
> R4#
>
> try to add the next-hop-self command but it didn't help much
>
> is it possible to make this topology works using only ibgp+ebgp ?
> am i missing something here ?
>
>
>
> ---------------------------------
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-- Narbik Kocharians CCIE# 12410 (R&S, SP, Security) CCSI# 30832 www.Net-WorkBooks.com
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