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Trouble with linking across a DWDM

I have Brocade 2800 SAN switches, one at location X and one at location Z. The sites are approximately 5K apart. I attempted to link the two switches using our dedicated dark fiber across a DWDM system. Each of the line cards I am using is specified for 850nm fiber. It failed. I was told that it might be because I was using short haul GBICs. But the GBICs and band cards are rated for 850nm so it shouldn't be an issue.

Is there some configuration feature that I need to set? Or anything else I can do to establish these links across DWDM?

Please advise.


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I think your problem is related to how your connections are set up.

Here are the specs for fiber connections:

Shortwave (850 mm) GBIC using 50u cables have a maximum distance or 500 meters between end devices.

Longwave (1300 mm) GBIC using 9u cables have a maximum distance of 10 kilometers between end devices without an extender/repeater.

Using DWDM on "dark fiber" (9u cables) the distance can be extended to up to 100 kilometers between end devices.

So for you to create an extended fabric between your sites at 5Km apart, your configuration should look like this:

Host to switch=50u Multi-Mode Cable to short wave GBIC (850mm)
Switch host port uses short wave GBIC (850mm)
Switch to DWDM= 50u Multi-Mode cable to short wave GBIC (850mm)
DWDM to remote site connection=long wave GBIC (1300mm) to 9u single-mode cable (dark Fibre).

Your line cards have short wave multi-mode connections. That's fine for the local connections, but you need longwave single mode connections for the link between the sites.

You would have the same setup on the remote side. You may also need the SAN extension license for your switches as that pumps up the number of available buffer credits between the switches.

Chris

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This was first published in July 2002

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