Looping Issue

Unanswered Question
Nov 12th, 2009

Hello Netops,

Need help to resolve this issue.We are getting the logs of looping on our switch.


Nov 9 19:11:06.562: %IP-3-LOOPPAK: Looping packet detected and dropped

- src=, dst=, hl=20, tl=32, prot=17, sport=7,

dport=48971 in=Vlan701, nexthop=, out=Vlan701 options=none -Process= "IP Input", ipl= 0, pid= 109 -Traceback= 406F2BD8 406F2E84

406F3648 406E486C 406E5BC8 406E3B6C 406E3D68 406E4



And as per the routing table its showing its a directly connected.

NLOSSKR1B01#sh ip route

Routing entry for

Known via "connected", distance 0, metric 0 (connected, via interface)

Redistributing via ospf 101

Advertised by ospf 101 metric-type 1 subnets route-map single-path

Routing Descriptor Blocks:

* directly connected, via Vlan701

Route metric is 0, traffic share count is 1


Dont know whr exactly the issue..please help.

One more log this might help you to find the resolution.

NLOSSKR1B01#sh arp | i

Internet 2 0021.9b89.c0bb ARPA Vlan701



Manish Prasad

I have this problem too.
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Giuseppe Larosa Thu, 11/12/2009 - 13:41

Hello Manish,

error message decoder provides the following suggestion:

1. %IP-3-LOOPPAK: Looping packet detected and dropped - src=[int], dst=[int], hl=[int], tl=[int], prot=[int], sport=[int], dport=[int] in=[chars], nexthop=[int], out=[chars]options=[chars]

A looping packet has been detected. A very common cause is 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.

Recommended Action: Analyze the source and destination addresses of the looped packets and verify that the configuration of the IP helper addresses in the router is correctly pointing to the proper device and is not pointing to the router itself.

Hope to help



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