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Webcast-Catalyst9k
New Member

fibre link issue

I have a fibre link that passes all of the generic fibre tests, icluding the 1000baseLX and SX tests. However when I connect switches to the link I only get a LINK LED on one side.

Here are the test I did.

I connected a cisco 2950 switch in Location A to the Nortel in location B. The Nortel would get a link light but the cisco would not.

When I connect a nortel switch in location A to a linksys in location B, the linksys gets a link light, but the nortel does not.

When I connect the 2950 in location A to the linksys location B, neither gets a link light. The linksys link light will flash the instant the fibre is inserted, but goes back off immediately and stays off.

I then got a media converter and added to the equation

The MC would get a link light when connected to the nortel, but the nortel, would not get a link light.

When the MC is connected to the cisco neither gets a light

When the MC is connected to the linksys, the MC gets a light but the lilnksys does not.

Under what circumstances would you get a link light on one side of a fibre link and not the other.

2 REPLIES
New Member

Re: fibre link issue

In my experience, the one time that happened to me, it was because there was a problem in one strand of the fiber. So one switch could send but the other could not. The explanation given to me was that a switch only needs to see traffic sent from the other for the link light to come on.

So if switch A can send to B but B cannot send to A, you will get a link light on B but not on A.

New Member

Re: fibre link issue

You are probably right about that. I can get the linksys to display the link light with only one fibre connected.

Although the linksys and nortel switches will display link light under certain circumstances, the 2950 never does.

Also both fibres pass the fibre channel test at gigabit speeds.

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