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I am a novice cisco user and I am trying to investigate as to why one of our connections went down.

We have a fiber network ring that is operating just fine. Connected to this ring via ethernet, is a lone 3560. This connection has worked flawlessly for the past year and a half. This morning, I noticed that I could not connect to that remote switch.

I checked the configurations on both switches, and nothing has changed (as I expected). In the field, the port lights were flashing, indicating that some sort of communication is occurring. There is only 1 ethernet cable that has been run between these two locations, so testing an alternate path is not possible.

What else can I do to fix this connection?

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Not that I'd recomend it as a first course of action, but I've run into some inexplicable connection issues with Cisco switches that had 400+ days of uptime that were cleared up by a reload. (Make sure your configs are saved first, obviously.) – HopelessN00b Jun 20 '12 at 14:17
Hmm... Possibly some sort of memory is getting full? I never considered it, but it is definitely possible. Thanks for the tip. – kubiej21 Jun 20 '12 at 14:44
that exact thing happened to me on a ASA5510. After a year of uptime, I could no longer connect to the ASDM. Tech support said that was a known issue with my particular version and once I rebooted it, I could connect. – August Jun 20 '12 at 15:28

Turns out it was a dead port. I tested this by first resetting the counters, and then by examining the port itself. The counters indicated that the port was sending out packets, but wasn't receiving any.

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