Fiber link fails to pass traffic.

Unanswered Question
Sep 29th, 2007


I am a Systems Engineer working with a Cisco Channel Partner.

A client of ours has a fiber backbone between two buildings on their campus.

The fiber terminates on a Catalyst 6509 (at the data centre) and a Catalyst 3750 at the other end. Users at the far-end connect to servers located at the data center over this fiber.

This connection has been working fine for the past 2 years, until a recent problem came up.

For two weeks now, the usual occurrence is for the fiber link to stop passing traffic while working until the 3750 is rebooted or the fiber connectors removed from the SFP port and replugged.

Meanwhile, the interface and line protocol remain UP on both switches during this abnormal behaviour. There are also no log messages occurring. Everything look fine on both switches. They just wouldnt pass traffic. The problem occurs about twice each day.

It's difficult diagnosing the problem now. I need help pls.



I have this problem too.
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tphelps Sat, 09/29/2007 - 17:49

I would do a few things:

1. Scope and clean the fiber

2. Measure all TX and RX levels with a power meter

3. Perhaps replace the SFPs


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