GLC-GE-100FX= SFP in 2960S-24TS-L only running half-duplex

Answered Question
Apr 20th, 2011

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We run a 100 Mbit trunk over 62.5 MM fiber to a remote building. We replaced the building’s single switch.

Old:

2950C-24 switch with integrated 100BASE-FX optic using a MTRJ to SC fiber patch

New:

2960S-24TS-L and GLC-GE-100FX= SFP optic with LC to SC fiber patch

Since the install, the link will only connect at half-duplex 100 Meg. It will not link when forced to full duplex. The other end is a 6324-100FX-MM module in our 6509. No duplex mismatch issues prior to the new switch, optic and patch. We measured only 4-5 dBm loss at each end point with our fiber owl. To rule out the fiber path, I duplicated the problem with an identical 2960 switch and optic over a 2-meter LC/LC patch to the 6509. I also tried a 2-meter LC/LC patch between these optics in the same 2960 switch, again only half-duplex.

http://www.cisco.com/en/US/docs/interfaces_modules/transceiver_modules/compatibility/matrix/OL632702.html

- suggests compatibility with the 2960S-24TS-L and the switch recognizes the SFP and appears to function normally other than the duplex issue.

Not sure why we seem to be stuck at half-duplex. Any thoughts or suggestions are much appreciated, thanks!

I have this problem too.
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Correct Answer by Tom Randstrom about 3 years 1 day ago

Have you tried to "no duplex" on each end and then reset each end to "duplex auto" or "duplex full"?  You might also try to remove/reinsert the transceiver at the 6500 end and see if this clears the problem.

Very odd situation.   

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Correct Answer
Tom Randstrom Thu, 04/21/2011 - 07:00

Have you tried to "no duplex" on each end and then reset each end to "duplex auto" or "duplex full"?  You might also try to remove/reinsert the transceiver at the 6500 end and see if this clears the problem.

Very odd situation.   

mrdorshimer Thu, 04/21/2011 - 07:32

so far so good...

"no duplex" followed by "duplex full" has worked on my test bench, from a 2960 to 6509 and between a pair of 2960's. I will test in production shortly and report back.

Update:

That suggestion works in production. Have you seen something similar before? I don't think I've ever had to "no duplex" a port/optic before it would run at auto or full properly.

Thanks!

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Posted April 20, 2011 at 5:18 PM
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