Link two 3500 switches together. No green lights.

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Jun 7th, 2006
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I'm trying to setup a 3500 8 port fibre switch to link into the network. I have set up IP address and gone through the default config. Then inserted GBIC module and linked directly into another 3500 8 port fibre with a fibre cable but not getting green lights at either end of the connection.

What's the most likely cause of failure in this scenario. The GBIC's, the cable or the switch config itself. What tests can I run to troubleshoot.

Many thanks


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Overall Rating: 4 (4 ratings)
peterledwidge Wed, 06/07/2006 - 10:16
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have you tried swapping the fibre connections around at one end. Both devices are the same so the

transmit and receive connections must be the correct

way around - like a cross over lead.


Roberto Salazar Wed, 06/07/2006 - 11:35
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Make sure that the fiber from one end is crossed to the other end. For example, switchA <--< SwitchB, switch A>-->SwitchB. I am trying to show the rx and tx of the connectors, if one side is rx it shoud tx on the other side. Other than the LED, what is the status of the interface? down/down, up/down?

Try setting the speed option to auto (assuming that it was statically set before). Also, make sure you did not use the nonegotiate command on the actual switchport.

Are these brand new gbics or are they used?

Did you shine light down your fiber patch cable to make sure there are not breaks or severe microbends in it? Hope this helps.

leighharrison Thu, 06/08/2006 - 03:06
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Hi there,

If you type the command "sh interface status" it will tell you if it can see the Gbic and what type it is. As there is no light, that would point towards a layer 1 error.

You need to ensure that:-

1. The switches can see the gbics.

2. They are both 1000mb ports (I've had problems in the past trying to connect 100mb ports to 1000mb ports)

3. The fibre is clean and not broken

4. You connect transmit to recieve on the fibres.

Please rate helpful posts,

Hope this helps a bit,



NealMatthews Fri, 06/09/2006 - 06:33
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Hello everyone.

Thnaks for some great feedback on this conversation. I have replaced the SC/SC cable and my new cable happily gives me a green light on both ports.




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