Problem with loopback interface

ccallison · ‎06-25-2015

I'm trying to set up a loopback interface with a routable address and I don't see what is wrong. I've already set up one up that is working perfectly and now the second one isn't working.

ip vrf AWS-EUTEST-VPN
rd 65002:103
route-target export 65002:103
route-target import 65002:103
!
ip vrf US-WEST-CA-MONITORING
rd 65001:101
route-target export 65001:101
route-target import 65001:101
!
interface Loopback101
ip vrf forwarding US-WEST-CA-MONITORING
ip address 173.209.243.118 255.255.255.255
!
interface Loopback103
ip vrf forwarding AWS-EUTEST-VPN
ip address 173.209.243.119 255.255.255.255
!
interface GigabitEthernet0/0
ip address 173.209.243.117 255.255.255.240
!
ip route 0.0.0.0 0.0.0.0 173.209.243.113
ip route 173.209.243.118 255.255.255.255 Loopback101
ip route 173.209.243.119 255.255.255.255 Loopback103
ip route vrf US-WEST-CA-MONITORING 0.0.0.0 0.0.0.0 173.209.243.113 global
ip route vrf AWS-EUTEST-VPN 0.0.0.0 0.0.0.0 173.209.243.113 global

I can ping back and forth from the gi0/0 to Loopback101, but not from gi0/0 to Loopback103.

There is an error logged when I try to ping Loopback103:

Jun 25 2015 11:23:11.373 PDT: %IP-3-LOOPPAK: Looping packet detected and dropped -
src=173.209.243.119, dst=173.209.243.119, hl=20, tl=100, prot=1, sport=0, dport=0
in=Loopback103, nexthop=173.209.243.119, out=Loopback103
options=none -Process= "IP Input", ipl= 0, pid= 175
-Traceback= 3221BE5Cz 30142B50z 301431F0z 30144084z 30144564z 3013E288z 301453CCz 3013EBC0z 3013EE48z 3013EF28z 3013F164z 332EE1C8z 332EE1ACz

Mark Malone · ‎06-26-2015

Looks like software crash as there is traceback logs , here is the output for that alert belowYou really need to contact TAC to decode the traceback find out exactly what function crashed it

The %IP-3-LOOPPAK: Looping packet detected and dropped error message is received because of a looping packet that has been detected. A common cause is a misconfiguration of an IP helper address. The helper address should be the same address as that of the server of the intended service. Putting the address of the router in the helper address causes a routing loop to be created.

The recommended action is to analyze the source and destination address of the looped packets and verify that the configuration of the IP helper addresses in the router correctly points to the right device and does not point to the local router itself.

The %IP-3-LOOPPAK: Looping packet detected and dropped error message is received because of a looping packet that has been detected. A common cause is a misconfiguration of an IP helper address. The helper address should be the same address as that of the server of the intended service. Putting the address of the router in the helper address causes a routing loop to be created.

The recommended action is to analyze the source and destination address of the looped packets and verify that the configuration of the IP helper addresses in the router correctly points to the right device and does not point to the local router itself.

- See more at: https://supportforums.cisco.com/discussion/10960711/ip-3-looppak-looping-packet-detected-and-dropped#sthash.3VQCV7XK.dpuf

ccallison · ‎06-30-2015

Isn't it a little weird that one loopback associated with that physical interface works perfectly, but the other one doesn't?

Nevertheless, I will open a TAC case about it....