Re: show ip bgp

Danilo Dy · ‎04-11-2007

Hi,

I need some light about the "show ip bgp" output in one of my router.

RT2# show ip bgp

BGP table version is 2, local router ID is 192.168.0.253

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

* i192.168.0.0/20 192.168.0.252 0 100 0 i

* i 192.168.0.254 0 100 0 i

*> 192.168.0.141 20 32768 i

RT2#

192.168.0.141 is not running BGP but OSPF. Why would the "show ip bgp" choose it as best?

IOS is 12.4(10b) ADVANCED ENTERPRISE SERVICES

jpl861 · ‎04-11-2007

What is 192.168.0.141? Do you have a network diagram?

-John

Jon Marshall · ‎04-11-2007

Hi Danilo

I'm not sure of your topology so i could be wrong but it looks like the route for 192.168.0.0/20 is being learnt from both EBGP and also the IGP which in your case is OSPF.

A route learned from EBGP gets a weight of 0. A route learned from the IGP gets a weight of 32768. Weight is used above all else to determine which route to insert into the routing table.

We have the same issue here where i work and we add 40000 to the EBGP learned route to ensure that is the route inserted into the routing table.

Do you have a network statement for 192.168.0.0/20 on your RT2 router.

HTH

Jon

Danilo Dy · ‎04-11-2007

Hi All,

Thanks for your replies.

Jon, your right its IGP/OSPF. When I execute "show ip bgp", I'm expecting only BGP (eBGP/iBGP) routes not EGP/IGP routes so I was surprise to see IGP/OSPF learned routes in the "show ip bgp" output. The output of "show ip bgp" in RT1 and RT3 is different though. I'm curious whether local traffic will loop as I noticed some funny bandwidth utilization in R3 interface connected to R2 and SW3. I'll post R1 and R3 output tomorrow.

I'm currently in the internet cafe now so I can't post a decent diagram.

# Connections

R1 crossed-cable to R2

R2 crossed-cable to R3

R1 GRE Tunnel to R3

SW1 patch cable to R1

SW2 patch cable to R2

SW3 patch cable to R3

SW1 crossed-cable to SW2

#Loopback0 IP Address and use

R1/loopback0(BGP/OSPF source)=192.168.0.254

R2/loopback0(BGP/OSPF source)=192.168.0.253

R3/loopback0(BGP/OSPF source)=192.168.0.252

SW1/loopback0(OSPF source)=192.168.1.254

SW2/loopback0(OSPF source)=192.168.1.253

SW3/loopback0(OSPF source)=192.168.1.252

#HSRP

HSRP between R1/R2 and SW1/SW2

R1=192.168.0.130/28

R2=192.168.0.131/28

R1/R2-VIP=192.168.0.129

SW1=192.168.0.141/28

SW2=192.168.0.142/28

SW1/SW2-VIP=192.168.0.140/28

#BGP

R1 BGP Statement

!

router bgp 65123

bgp router-id 192.168.0.254

network 192.168.0.0/20

aggregate-address 192.168.0.0 255.255.240.0 summary-only

neighbor 192.168.0.252 remote-as 65123

neighbor 192.168.0.252 description BGP with RT3

neighbor 192.168.0.252 password secret

neighbor 192.168.0.252 update-source Loopback0

neighbor 192.168.0.252 version 4

neighbor 192.168.0.252 next-hop-self

neighbor 192.168.0.252 soft-reconfiguration inbound

neighbor 192.168.0.253 remote-as 65123

neighbor 192.168.0.253 description BGP with RT2

neighbor 192.168.0.253 password secret

neighbor 192.168.0.253 update-source Loopback0

neighbor 192.168.0.253 version 4

neighbor 192.168.0.253 next-hop-self

neighbor 192.168.0.253 soft-reconfiguration inbound

-removed_external_peer_statement-

maximum-paths 2

no auto-summary

!

R2 BGP Statement

!

router bgp 65123

bgp router-id 192.168.0.253

network 192.168.0.0/20

aggregate-address 192.168.0.0 255.255.240.0 summary-only

neighbor 192.168.0.252 remote-as 65123

neighbor 192.168.0.252 description BGP with RT3

neighbor 192.168.0.252 password secret

neighbor 192.168.0.252 update-source Loopback0

neighbor 192.168.0.252 version 4

neighbor 192.168.0.252 next-hop-self

neighbor 192.168.0.252 soft-reconfiguration inbound

neighbor 192.168.0.254 remote-as 65123

neighbor 192.168.0.254 description BGP with RT1

neighbor 192.168.0.254 password secret

neighbor 192.168.0.254 update-source Loopback0

neighbor 192.168.0.254 version 4

neighbor 192.168.0.254 next-hop-self

neighbor 192.168.0.254 soft-reconfiguration inbound

-removed_external_peer_statement-

maximum-paths 2

no auto-summary

!

R3 BGP Statement

!

router bgp 65123

bgp router-id 192.168.0.252

network 192.168.0.0/20

aggregate-address 192.168.0.0 255.255.240.0 summary-only

neighbor 192.168.0.253 remote-as 65123

neighbor 192.168.0.253 description BGP with RT2

neighbor 192.168.0.253 password secret

neighbor 192.168.0.253 update-source Loopback0

neighbor 192.168.0.253 version 4

neighbor 192.168.0.253 next-hop-self

neighbor 192.168.0.253 soft-reconfiguration inbound

neighbor 192.168.0.254 remote-as 65123

neighbor 192.168.0.254 description BGP with RT1

neighbor 192.168.0.254 password secret

neighbor 192.168.0.254 update-source Loopback0

neighbor 192.168.0.254 version 4

neighbor 192.168.0.254 next-hop-self

neighbor 192.168.0.254 soft-reconfiguration inbound

-removed_external_peer_statement-

maximum-paths 2

no auto-summary

#OSPF

R1/R2/R3/SW1/SW2/SW3 OSPF

!

router ospf 65123

router-id R1_R2_R3_SW1_SW2_SW3_loppback0_ip_address

log-adjacency-changes

redistribute connected subnets

redistribute static subnets

network 192.168.0.0 0.0.15.255 area 0