i got ICMP: time exceeded

Ibrahim Jamil · ‎02-25-2016

Hi guys

any loop on the below output , why i got ICMP: time exceeded , SW1 runs BGP ( privcate AS ) dual to 2 PE ( same provider ) with maximum path 2

SW1#traceroute 8.8.0.1
Type escape sequence to abort.
Tracing the route to 8.8.0.1
VRF info: (vrf in name/id, vrf out name/id)
1 172.16.102.2 1 msec
172.16.104.4 1 msec
172.16.102.2 1 msec
2 172.16.34.3 [MPLS: Labels 201/111 Exp 0] 11 msec
172.16.24.4 [MPLS: Labels 403/111 Exp 0] 15 msec
172.16.34.3 [MPLS: Labels 201/111 Exp 0] 10 msec
3 172.16.34.3 [MPLS: Labels 201/111 Exp 0] 15 msec
172.16.18.1 [AS 100] [MPLS: Label 111 Exp 0] 11 msec
172.16.34.3 [MPLS: Labels 201/111 Exp 0] 20 msec
4 172.16.18.8 [AS 100] 14 msec
172.16.18.1 [AS 100] [MPLS: Label 111 Exp 0] 16 msec
*Feb 25 03:14:49.057: ICMP: time exceeded rcvd from 172.16.102.2
*Feb 25 03:14:49.058: ICMP: time exceeded rcvd from 172.16.104.4
*Feb 25 03:14:49.059: ICMP: time exceeded rcvd from 172.16.102.2
*Feb 25 03:14:49.070: ICMP: time exceeded rcvd from 172.16.34.3
*Feb 25 03:14:49.085: ICMP: time exceeded rcvd from 172.16.24.4
*Feb 25 03:14:49.095: ICMP: time exceeded rcvd from 172.16.34.3
*Feb 25 03:14:49.110: ICMP: time exceeded rcvd from 172.16.34.3
*Feb 25 03:14:49.120: ICMP: time exceeded rcvd from 172.16.18.1
*Feb 25 03:14:49.141: ICMP: time exceeded rcvd from 172.16.34.3
*Feb 25 03:14:49.155: ICMP: dst (172.16.104.10) port unreachable rcv from 172.16.18.8
*Feb 25 03:14:49.171: ICMP: time exceeded rcvd from 172.16.18.1 *
SW1#

thanks all

Philip D'Ath · ‎02-25-2016

This happens when you have a routing loop. The packet TTL is decremented on every hop till it gets to zero and then you are sent an ICMP TIME EXCEEDED message, causing the above.