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New Member

3550 Switch underruns

Does anyone know what would cause this?

73498724 packets output, 230458162 bytes, 10032 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

10032 output buffer failures, 0 output buffers swapped out

The client hanging off this port is not another switch or any infrastructure equipment. It is, to the best of my knowledge, a standard user device - like a PC or industrial controller.


Re: 3550 Switch underruns

Underruns occur when packets are not retrieved quickly enough from shared memory to be transmitted. Probably just happened when he was doing some heavy download , clear the counters and watch it and ask the person if he is having any performance issues . I wouldn't worry about it too much.

New Member

Re: 3550 Switch underruns

Well, I'll take your advice and clear the counters. I'll watch it for the next few days. However, whatever device is on this port is running some critical monitoring application and the tech user who owns the box is complaining pretty often. He says he's dropping packets - notably.


Re: 3550 Switch underruns

Make sure the NIC drivers are up-to-date on the device.

If that still fails, replaces the NIC/Adapter/Interface.

It might be worthwhile to try another cable, and / or drop it to half-duplex and see if the nature of the problem changes.

Good Luck



Re: 3550 Switch underruns

Verify what his nic settings are set at . If they hardcoded then the switch must be hardcoded to the same setting . If it is at auto for speed and duplex the switch setting must also be auto for speed and duplex . If you do a show int status what does his port setting look like is it auto or hardcoded ?

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