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Fiber Connection between two Cisco 2960 Switches

First off, I'm a Fiber noob, so be gentle.

Company I work for just moved into a new location.  We have two data closets which are patched as independent entities, with no Ethernet tie connection. These closets are roughly 100 feet apart. 

There is a fiber connection that runs between both closets, that the previous tenant used to connect the switches.  I have placed a Cisco 2960 switch in each location, and added one mini SFP gbic's to each switch.  After attaching both sides, neither light up.  I do a sh inter gig1/0/49 on each and shows 'down down' (not admin down).

What is the trick on getting these to communciate, do I need to configure these ports, and are they supposed to light up? 

What I am trying to accomplish is to get the one closet that is completely cut off, communicating by logically stacking, or 'daisy chaining' via fiber. 

I turned off the lights and popped the fiber out, and I do see a faint red light (I did not look straight into it), so I think the fiber is active.

I am open ears to a sound fix.


Fiber Connection between two Cisco 2960 Switches

Generally the solution to this is to reverse the polarity of the fiber. On ONE end of your fiber connection (pick 1 room) reverse the transmit and receive of the strands. This can be accomplished by physically removing the 2 fiber strands out of their connector and switching the spot in which they are seated.

The purpose of this is to align the Transmit of one end with the receive on the other end.. My suspicion is that the Transmit on one end is lining up with the Transmit of the other end, resulting in no communication - This is a very common problem.

Try this and let me know.


Fiber Connection between two Cisco 2960 Switches


Good advice from Kyle. (+5)

Also worth checking that your SFP Gbics math the type of fibre cable and patch cords

Single mode or multimode



Regards, Alex. Please rate useful posts.
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