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Community Member

Etherchannel between 3550 and 2950

I am having problem configuring the etherchannel between these two switches.

3550 has two ports connected to 2950 (23and24). Show etherchannel on 3550 shows that everything is OK, channel is up, lights are green.

Show etherchannel on 2950 shows the same. All up. However, port 24 is amber and shut down. I get the message %ETHCNTR-3-LOOP_BACK_DETECTED on port 24 at 2950.

Any suggestions.


Re: Etherchannel between 3550 and 2950

From the messages manual I'd say you have a cable problem

Error Message ETHCNTR-3-LOOP_BACK_DETECTED:, Loop-back detected on [chars]. The port is forced to linkdown.

Explanation This message means that the loop-back condition might be caused by a balun cable being accidentally plugged into the port.[chars] is the port.

Recommended Action Check the cables. If a balun cable is connected and the loopback condition is desired, no action is required.

Otherwise, connect the correct cable, and bring the port up by entering the no shutdown interface configuration command.

Community Member

Re: Etherchannel between 3550 and 2950

I am not sure what is the problem, because cables are OK. The same config (physical layout, cables and config.file) worked just fine, and it works even today. Only thing I did diferently is that I turned on 3550 (being disconnected from the 2950s) and then plug each 2950 one by one, cable by cable and it seems to be working fine.

Last time it stoped working was after I powered off and on entire rack of switches. It seemed to behave differently if you power it on while the switches are connected.

Well, I am not sure what the cause is. However, it is working now. Thanks for the suggestions.

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