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Fiber connection between two 3com 4200g switches not working

Posted on 2009-04-03
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Last Modified: 2013-11-13
I have two 3com 4200g switches that I am trying to connect via 3CSFP92-AX mini-GBICs.
The people that ran the fiber ran it as single-mode and we have done light test from point-to-point and that goes well.

When plugged into the switch, the port status shows as Enable[InActive].
I'm not sure what else I need to do. The 4200g web management screen does not have much more port management and I'm at a loss. Need to get these two switches communicating and any help is appreciated.

Thanks.

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Question by:cwile
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8 Comments
 
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Expert Comment

by:jfrady
ID: 24064677
Have you tried switching the transmit/receive?  
Has the fiber been tested?
Have you tried the switches with just a jumper?
The most likely cause is physical layer - jumper, connector, transceiver, etc.

By it saying inactive it means there is no link.  

Start troubleshooting a piece at a time.
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Author Comment

by:cwile
ID: 24064804
I'll be honest, I'm not good at all with fiber/networking ;)

By switching the transmit and receive do you mean switching the wires coming from the wall to the switch on both ends? If so, i wrote down their original settings and tried switching each location one at a time with no avail, so I put them back to how they were originally installed.

I have not tried a jumper yet. I will try that next. I can't do that until monday though.

As far as tested, the company I had run the lines used a small tool that shot light through each connector and the other end did receive the light.

One thing that isn't sitting right in my mind is that when the GBIC is plugged in, the LED light above it is not lit up. I was also told the GBIC would have a light shining out of it when plugged in, but I do not see that either.

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Accepted Solution

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jfrady earned 1500 total points
ID: 24064919
It's not advisable to look into the transceiver to see if you see light.  The older LED driven optics weren't a problem but Laser driven optics can impair your vision instantly.  And singlemode connections are generally out of the visible light range.  If they tested just by shining light through that isn't much of a test. Just because you can see visible light doesn't mean the connection is within spec.   At minimum a dB loss reading should have been performed.  Even better is an OTDR trace.

Regardless, this doesn't mean the fiber is bad.  What I mean about transmit and receive - there are actually 2 strands of fiber that are required to make the connection.  A transmit and receive.  The transmit from side a goes to the receive on side b and vice versa.  The connector used with that transceiver is called LC.  At first glance it may not seem that you can reverse the individual strands of fiber but you can.  There is generally a clip of some sort that holds the LC connector together that you can flip off and reverse the strands.  This way you will be able to tell if transmit/receive is the issue.  I would give this a very high probability of being the cause.

I'm pretty sure the LED above the 3CSFP92 will not light until link is established.  

It's hard to guess not knowing more about your environment.  When you mention cables from the wall - do you mean the copper cables or fiber?  Did the folks that ran the fiber for you put connectors right on the end or did they terminate the fiber into a box or faceplate and then supply a fiber jumper to actually plug in to the switch?

Any details would help.  

If you have a fiber jumper you could take one of the switches and place it beside the other, connect it with the jumper, and rule out a defective switch, jumper, or fiber module.
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Author Closing Comment

by:cwile
ID: 31567502
The problem was the GBICs themselves. Apparently multi-mode GBICs don't work with single mode fiber. The one supplying my GBICs assumed multi-mode.

The other problem was the transmit/receive was wrong. Put in single-mode gbics and fixed the transmit/receive and all is fine.

Thank you :)
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Expert Comment

by:jfrady
ID: 24087332
Glad you got it worked out.  By the way - the first thing I thought of was that you had the wrong SFP module.  I verified though that the part number you listed though was for the singlemode model so  didnt mention that as a possibility.  What you actually had then must have been the 3CSFP91  
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Expert Comment

by:jfrady
ID: 24087342
Just thinking that should have been an A rated answer based on the info I had to go on.  ; )
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Author Comment

by:cwile
ID: 24087917
I thought I clicked A.
Anyway I can change that?
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Expert Comment

by:jfrady
ID: 24087946
Not sure.  Doesn't matter though.  I appreciate the points!  And glad you got the issue worked out!
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