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New Member

3550-48 Switch port loopback error

Hi,

I have a Catalyst 3550-48 [SMI] that has servers connected to it. The following error was logged to the Syslog server after trying to troubleshoot the server connection to port 46:

%ETHCNTR-3-HALF_DUX_COLISION_EXCEED_THRESHOLD: Collision at FastEthernet0/46 exceed threshold. Consider as loop-back.

What does this error specifically mean? Initially the switch port and the server connected to it were set for auto-negotiate but I changed the settings to 100 Mbps, full-duplex on both ends after noticing the error. However the switch port is still not functioning.

Please advise,

RAJ

4 REPLIES
Silver

Re: 3550-48 Switch port loopback error

Raj,

Error

Message ETHCNTR-3-HALF_DUX_COLISION_EXCEED_THRESHOLD:

Collision at [chars] exceed threshold. Consider as loop-back.

Explanation This message means that the collision at a half-duplex

port exceeded the threshold, and the port is considered to be in the

loop-back state. [chars] is the port.

Here's the URL:

http://www.cisco.com/en/US/partner/products/hw/switches/ps646/products_system_message_guide_chapter09186a008007ef4c.html#xtocid20365

Make sure you don't have a duplex mismatch on this port. Might be causing this.

Hope this helps you,

Don

New Member

Re: 3550-48 Switch port loopback error

Don,

Thanks. That's the explaination I also got when I used the Error message decoder tool. I am trying to get the switch port functioning again. Is there any command to turn off this loopback condition on the port or does the switch do that automatically after some time?

Also, when I perform the :

Switch# show interface f0/46

It shows loopback as "not set" which should mean that the port should operate normally, right?

Thanks,

RAJ

Silver

Re: 3550-48 Switch port loopback error

RAJ,

This is just a guess here since I don't have the needed information but I would imagine that the port is errdisable due to the errors in your logs. Either unplug this from the offending machine (might be a duplex mismatch causing this) correct the issue & reconnect. If IOS "not shut" if CATOS "set port enable" should get it working.

Hope this helps you,

Don

New Member

Re: 3550-48 Switch port loopback error

Hello Raj

Don have given you the good Url about your problem.

As he said :

HALF_DUX_COLISION_EXCEED_THRESHOLD: Collision at [chars] exceed threshold. Consider as loop-back.

Explanation This message means that the collision at a half-duplex port

exceeded the threshold, and the port is considered to be in the loop-back state. [chars] is the port.

Recommended Action No action is required.

but have you got this message :

Error Message ETHCNTR-3-LOOP_BACK_DETECTED:, Loop-back detected on [chars].

?

And is it possible to post the result of sh int f0/46 ?

We have already meet the phenomen at a customer but there were lot hubs behind the bad port that explain the high numbers of collisions.

The solution was to replace hub by switch to reduce collisions.

Anyway you don't only one server behind you fast0/46.

We have search a command to force the "no loopback detection" but it seems that such command doesn't exist.

Have you change your cable ?Or change the duplex and speed of server card?

Good luck.

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