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Unidrectional Port on Catalyst 3550-PWR

Unanswered Question
Jan 16th, 2004
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We have recently seen one of the copper switch ports on a Catalyst 3550-PWR enter a 'unidirectional' state where the output of "sh counters" shows traffic being transmitted by the port, but not any received traffic. (The equipment plugged into the switch was not at fault as it was plugged into another port, and bi-directional traffic flow was observed).


A reload of the switch seems to have cured the problem, but I was wondering whether this has been elsewhere and whether it is indicative of an underlying problem with the switch. The switch is running IOS 12.1(13)EA1c.

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peterjhill Fri, 01/16/2004 - 13:36
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When you say "unidirectional" I am guessing you are not talking about UDLD, as that will not work between a switch and a host. When the interface says it has not received any traffic, it means that no data from the host is being seen by the switch. Are you using the same patch cables all around? If you are near the limit of Cat5 and your cables are not twisted all the way to the end, you could easily see problems as you describe. You checked moving the equipment to a different port, I would also check a different piece of equipment on the same port before thinking it was a problem with the 3550.

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