2960G - SFPs - Unable to connect 2 Switches

[GRANT3779]

Hi All,

Trying to connect 2 switches together (both 2960G 8 ports). I have an SFP in each (GLC-LH-SM). They are connecting over SingleMode Fibre using the correct cabling. The fibre cores have been tested and are all ok also.

I can't get no Layer 1 connectivitiy at all. Just dead. I have tried 4 different GBICS, swapped cabled etc.. I have forced the media type to use SFP. No link light....

Am I missing something here? I thought it would just be a case of plugging in the gbics cables and off I go! I read about forcing the speed and duplex on the port but because the port if SFP, the speed and duplex settings are not available. This seems to be hard coded.

Any ideas??

Thanks

[Velimir Filipov]

It depends on the SFP what will be the speed.

Have you tested connecting some other devices through that fiber ?

How long is the fiber ?

Have you tried connecting the two switches with a patch cord ?

Are the SFPs Cisco ?

Do the switches detect them ?

[GRANT3779]

Hi Velimir,

We have testes connecting successfully 2 x 3750s over the same fire cores using 10GB SFPs, so cores between the buildings do work.

Fibre length between 2 switches is around 450m. I have read these SFP should be able to go 10km?

I managed to connect the switches successfully using copper in the same building, but I need to get them working over single mode cores.

SFPs are Cisco. When doing a show inventory the SFPs are recognised....

It's very puzzling!

[Velimir Filipov]

Have you tried connecting the two switches (2960) with a fibre patch cord (1 or 2 metre long)? If you do that - maybe it will be best to use some attenuators, in case the SFPs transmit with too high power.

The SFPs are using two separate fibers for each direction, right ? I guess you tried switching the pair on any of the sides.

Even the fibers was working with a 10GB SFPs, there is still a small chance that they have some attenuation or refraction (even they are very short in distance), and that might be just the problem.

Also its not a bad thing to try these SFPs on some other devices. Maybe those switches just won't work with that particular SFPs (which is highly doubtful).