04-23-2009 10:51 PM - edited 03-06-2019 05:21 AM
hi expert here,
i have a problem with the keepalive loopback cause the port error disable.
error logs like below:
%ETHCNTR-3-LOOP_BACK_DETECTED: keepalice packet loop-back detected on
| GigabitEthernet 0/11"
After some investigation, i know that this due to the Keepalive packet source & destination interface having the same address.
And the workaround solution provide by cisco is to disable the keepalive from the related interface. it works fine now.
But i still want to know why cause the Keepalive packet source and destination having the same address.
04-23-2009 11:58 PM
Hello Frankie,
the keepalives having the same source and dest MAC address = port MAC addresses are correct.
The problem is caused by a Cisco IOS bug where a wrong implementation may treat sometimes the event of receiving back keepalive frames as bad news and sign of a loop.
for keepalive frame format see
cisco@groupstudy.com/msg65904.html')">http://www.mail-archive.com/cisco@groupstudy.com/msg65904.html
The bug affects some IOS releases on some switch platforms on fiber based ports.
see this thread
http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=LAN%2C%20Switching%20and%20Routing&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40^1%40%40.2cc1ebcc/5#selected_message
you may need to copy to browser the text to be able to open the link
you can find this using search box on the top right with key LOOP_BACK_DETECTED
Hope to help
Giuseppe
04-24-2009 12:39 AM
Hi Giuseppe,
Many thanks for your help. It seems like upgrade the switch IOS version to 12.2(x) will solved the problem permanently.
BR,
Frankie
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