03-03-2009 12:20 PM - edited 03-06-2019 04:21 AM
Hi,
In a remote office I have a 3650 and from it's 0/24 port there is a trunk to a Nortel switch. The Nortel switch has no managment (just out of the box). Anyway from time to time the trunk will shutdown and get this error:
sh log | inc 0/24
1w6d: %PM-4-ERR_DISABLE: loopback error detected on Fa0/24, putting Fa0/24 in err-disable state
Somebody suggested the possible reasons can be a link flapping, UDLD just to mention twom but these mean nothing to me :)
Any ideas?
03-03-2009 12:42 PM
The message means the switch saw its own keepalive coming via a different port. This is a sign that multiple ports from the 3560 are connected to the Nortel switch.
Since this switch has no management, I recommend plugging just one port from the 3560 to the Nortel switch in order to avoid any loops.
See the explanation on this link regarding 'loopback error'
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00806cd87b.shtml#topicsub1
HTH,
__
Edison.
03-03-2009 01:04 PM
Thanks, but if I do a show ip int bri, the 3650 only shows 0/1 and 0/24 as up, 0/1 is the WAN port and 24 the trunk.
03-03-2009 01:09 PM
Try "sh interface 0/24 status" or "sh interface status err-disabled".
03-03-2009 01:10 PM
You can disable keepalives on the port connected to the Nortel switch.
You need to upgrade to 12.2SE in the 3560 switch.
03-03-2009 01:35 PM
I'm on 12.2(35)SE5
03-03-2009 01:37 PM
Then disable keepalive on that interface:
http://www.cisco.com/en/US/docs/ios/interface/command/reference/ir_i1.html#wp1014303
HTH,
__
Edison.
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