%IPRT-3-RIB_LOOP: Resolution loop formed by routes in RIB

Dipesh Patel · ‎05-10-2013

Dear Experts,

During the BGP configuration activity, I have faced an issue.

Topology :

Configuration :

TATA and Airtel Router are configured with VRRP
TATA and Airtel Router are configured with iBGP
Airtel configured as secondary using as-prepend.

When Problem faced :

When We have connected Vodafone link in to network and configured iBGP with only TATA not with Airtel.

What problem we have faced ?

From the LAN we are unable to reach TATA LAN Interface of the Router and outside network is not reachable from none of the routers.

Logs found in the TATA router :

May 10 17:18:37: %PARSER-5-CFGLOG_LOGGEDCMD: User:muparmar logged command:router bgp 65418
May 10 17:18:37: %PARSER-5-CFGLOG_LOGGEDCMD: User:muparmar logged command:neighbor 10.0.46.180 remote-as 65418
May 10 17:18:38: %PARSER-5-CFGLOG_LOGGEDCMD: User:muparmar logged command:neighbor 10.0.46.180 password *****
May 10 17:18:38: %PARSER-5-CFGLOG_LOGGEDCMD: User:muparmar logged command:address-family ipv4
May 10 17:18:38: %PARSER-5-CFGLOG_LOGGEDCMD: User:muparmar logged command:neighbor 10.0.46.180 activate
May 10 17:18:38: %PARSER-5-CFGLOG_LOGGEDCMD: User:muparmar logged command:neighbor 10.0.46.180 next-hop-self
May 10 17:18:39: %PARSER-5-CFGLOG_LOGGEDCMD: User:muparmar logged command:exit-address-family
May 10 17:20:11: %BGP-5-ADJCHANGE: neighbor 10.0.46.180 Up
May 10 17:36:44: %BGP_SESSION-5-ADJCHANGE: neighbor 10.0.46.103 IPv4 Unicast topology base removed from session BGP Notification sent
May 10 17:37:03: %BGP-5-ADJCHANGE: neighbor 10.0.46.180 Down BGP Notification sent
May 10 17:37:03: %BGP-3-NOTIFICATION: sent to neighbor 10.0.46.180 4/0 (hold time expired) 0 bytes
May 10 17:37:03: %BGP_SESSION-5-ADJCHANGE: neighbor 10.0.46.180 IPv4 Unicast topology base removed from session BGP Notification sent
May 10 17:37:34: %PARSER-5-CFGLOG_LOGGEDCMD: User:pachchigart logged command:interface GigabitEthernet0/0
May 10 17:37:37: %PARSER-5-CFGLOG_LOGGEDCMD: User:pachchigart logged command:no shutdown
May 10 17:37:39: %LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to reset
May 10 17:37:40: %VRRP-6-STATECHANGE: Gi0/0 Grp 10 state Init -> Backup
May 10 17:37:40: %IPRT-3-RIB_LOOP: Resolution loop formed by routes in RIB
May 10 17:37:42: %LINK-3-UPDOWN: Interface GigabitEthernet0/0, changed state to up
May 10 17:37:43: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up
May 10 17:37:43: %VRRP-6-STATECHANGE: Gi0/0 Grp 10 state Backup -> Master
May 10 17:38:25: %BGP-5-ADJCHANGE: neighbor 10.0.46.103 Up

TATA Router config :

router bgp 65418
bgp log-neighbor-changes
neighbor 10.254.251.14 remote-as 4755
neighbor 10.0.46.103 remote-as 65418
neighbor 10.0.46.180 remote-as 65418
!
address-family ipv4
network 10.254.251.12 mask 255.255.255.252
network 10.254.254.20 mask 255.255.255.252
network 10.254.254.152 mask 255.255.255.252
network 10.0.40.0 mask 255.255.248.0
network 10.0.48.0 mask 255.255.252.0
network 10.16.4.0 mask 255.255.252.0
network 10.16.8.0 mask 255.255.248.0
network 10.16.16.0 mask 255.255.240.0
network 10.16.32.0 mask 255.255.240.0
network 10.16.104.0 mask 255.255.248.0
network 10.20.66.0 mask 255.255.255.0
network 10.20.67.0 mask 255.255.255.0
network 10.21.155.0 mask 255.255.255.0
network 10.21.156.0 mask 255.255.252.0
network 10.21.160.0 mask 255.255.254.0
network 10.21.162.0 mask 255.255.255.0
network 10.25.0.0 mask 255.255.224.0
network 10.25.32.0 mask 255.255.224.0
network 10.25.64.0 mask 255.255.224.0
neighbor 10.254.251.14 activate
neighbor 10.254.251.14 filter-list 1 out
neighbor 10.0.46.103 activate
neighbor 10.0.46.103 next-hop-self
neighbor 10.0.46.180 activate
neighbor 10.0.46.180 next-hop-self

no auto-summary
exit-address-family
!

Airtel Router config

router bgp 65418
no synchronization
bgp log-neighbor-changes
network 10.0.40.0 mask 255.255.248.0
network 10.0.48.0 mask 255.255.252.0
network 10.25.0.0 mask 255.255.224.0
network 10.25.32.0 mask 255.255.224.0
neighbor 100.100.100.85 remote-as 9730
neighbor 100.100.100.85 allowas-in 10
neighbor 100.100.100.85 route-map RM-LOCAL-OUT-AIRTEL out
neighbor 100.100.100.85 filter-list 1 out
neighbor 10.0.46.102 remote-as 65418
neighbor 10.0.46.102 next-hop-self
no auto-summary

Vodafone Router (No Network advertisement done)

router bgp 65418
no synchronization
bgp log-neighbor-changes
neighbor 10.10.10.85 remote-as 55410

neighbor 10.10.10.85 route-map RM-LOCAL-OUT-AIRTEL out
neighbor 10.10.10.85 filter-list 1 out
neighbor 10.0.46.102 remote-as 65418
neighbor 10.0.46.102 next-hop-self
no auto-summary

Please help to resolve this issue.

At present we have restored the connectivity and kept TATA and Airtel router only.

(Vodafone Router is out of Network.

Regards

Giuseppe Larosa · ‎05-12-2013

Hello Dipesh,

if I have correctly understood you have three border routers, each of them connected to a different upstream ISP TATA, Airtel and the new one Vodafone.

iBGP sessions need to be full meshed or one device has to act as route reflector server for the other two.

The iBGP split horizon rule does not allow to propagate an iBGP route to another iBGP session.

So you need to solve this lack of iBGP sessions.

On Airtel router add

router bgp 65418

neighbor 10.0.46.180 remote-as 65418

neighbor 10.0.46.180 next-hop-self

On vodafone router

router bgp 65418

neighbor 10.0.46.103 remote-as 65418

neighbor 10.0.46.103 next-hop-self

Note: I have assumed from your configuration that the following router to IP address relationship exists:

TATA 10.0.46.0.102

Airtel 10.0.46.103

Vodafone 10.0.46.180

if it is different adapt to real IP addresses the suggestions that I have reported above

Edit:

I think that the error message is closely related to the lack of the necessary iBGP sessions between airtel and vodafone router that is detected by the tata router. Fix the issue first and the error message should disappear.

Hope to help

Giuseppe