Trunk port in "err-disable state"

whiteford · ‎03-03-2009

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?

Edison Ortiz · ‎03-03-2009

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.

whiteford · ‎03-03-2009

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.

Leo Laohoo · ‎03-03-2009

Try "sh interface 0/24 status" or "sh interface status err-disabled".

Edison Ortiz · ‎03-03-2009

You can disable keepalives on the port connected to the Nortel switch.

You need to upgrade to 12.2SE in the 3560 switch.

whiteford · ‎03-03-2009

I'm on 12.2(35)SE5

Edison Ortiz · ‎03-03-2009

Then disable keepalive on that interface:

http://www.cisco.com/en/US/docs/ios/interface/command/reference/ir_i1.html#wp1014303

HTH,

__

Edison.