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troubleshooting fiber link

dwyee3436
Level 1
Level 1

The school I work at upgraded to Cisco Catalyst 2960-S switches, all connected to each other via fiber.  I am seeing a problem with one such connection.  Cisco Network Assistant showed a "4-Warning" regarding the fiber link port: port was disabled because it was fluctuating between up and down too rapidly.  Possible hardware problem, resolve and re-enable.  (I'm paraphasing the message...it was 'acknowledged', and I can't bring it back up.)

This message was only showing on our "SV-Copy-Rm" switch's port 49.  The other end, on "SV-Maint-Rm" port 49 showed a normal green link status.

Using Internet Explorer, I logged onto SV-Copy-Rm switch's Device Manager, and  I first tried disabling/re-enabling port 49 on SV-Copy-Rm.  It came back up blinking yellow and showing "port has bad link" when I cursor hovered over port 49.  This continued for a few minutes, followed by port 49 being disabled again.

The current thing I'm trying is swapping the connection on both ends to a spare pair of fibers.  I'm pretty certain I've swapped to the same pair on both ends, however, now neither switch shows an active link.  I've disabled/enabled the ports on both ends, but still no link.

Question: How do I re-establish the above link? (The active connection has 'fallen back' to the designated ethernet Cat 5e connection and is currently running with that connection.)

1 Reply 1

Reza Sharifi
Hall of Fame
Hall of Fame

If there is no link light on either switch and you know for sure the fiber and the optics are good, than try switch the TX, and RX on one side of the connection.

HTH

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