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Problems configuring 10.GB llinks?


Hi I am in desperate need of help. We are trying to connect a Cisco 3750X 10GB port to a  Cisco 3560 12 port (10GB) Fibre Switch. The cable we are using is a 3M type single mode fibre cable. Both ports are configured as trunk ports and the GBICS we are using is certified as a 10GB GBICS. The prolem however is that the ports stays in a down down state. I have tried everything but the link does not come up. Does anyone know what I am missing or what I am doing wrong? Please help!!!!!                   

4 Replies 4

Giuseppe Larosa
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Hello Theunis,

what type of SFP are you using?

what is the distance between the switches?

Hope to help



hi Guiseppe

Thanks for the quick reply. It is SFP+ as far as I can see. The cable is a single mode fibre approximately 1 meter long. The switches are less then a meter appart. If it helps inanyway. These are the modules on the 3569:

and these are the modules on the 3750:


Hello Theunis,

>> The cable is a single mode fibre approximately 1 meter long

This can be the root cause the switches are very close to each other. The risk is that the optical receiver is saturated and it cannot correctly discriminate power levels of the signal.

It is important to know the exact type of SFP you are using. If the setup is permanent you should have thought of using multi mode fiber because SFP for MM are less expensive.

show inventory command provides also the part number of SFPs or you can read the part number directly on the SFP they can be inserted and removed with no issues.

If you are testing in a lab for preproduction, you may need an optical attenuator to reduce the optical power received

Hope to help


Thanks for the help so far. I appologize for all the questions. I wont be able to get the exact models untill tomorrow, but what I do have is the following:

The 3560 is a WS-C3560E-12D-S with 12 10GBASE X2 modules.(Not certain about the LR or SR)

The 3750 is a 3750e with two SFP-10GB-(Not certain about the LR or SR portion)

By a long shot would the LR modules on the 3750 be compatible with a SR module on the 3560?

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