In one of our plants, we've got an issue with the SFP, where we are not able connect two 2960s via a Fiber Link. My question is: are there any configation options, that can prevent the link to go up? (except media-type RJ-45)
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As far as I am concerned, the most common SFP problems are Poor performance, No connectivity and Corrupted software.
For the first one, the possible cause of this problem include that cabling distance is exceeded or port statistics show excessive frame check sequence (FCS), late-collision, or alignment errors.
Resolution: Reduce the cable length to within the recommended distances. See your SFP module documentation for cabling guidelines.
For the comnectivity issue, maybe you have used the incorrect ot bad cable, or STP (Shielded Twisted Pair) checking for possible loops.
Resolution: Verify the pinouts are correct for the proper application of cables. Replace the cable with a tested good cable. Wait 30 seconds for the port LED to turn green.
For the third issue—corrupted software, this include three situation including the port is placed in error-disabled state after SFP is inserted, device does not recognize the SFP module, and excessive errors found in port statistics.
Resolution: Remove the SFP module from the switch and replace it with a Cisco-approved module. Use the irrdisable recovery cause GBIC-invalid global configuration command to verify the port status, and enter a time interval to recover from the error-disable state. The best advice is to use the Cisco original SFP or 100% Cisco compatible SFP (If you decide to use a third-party SFP, please ensure that your supplier is assured) that is adapted to the switch.
Hope this might help you!