I have two sites with 5300s connected with FC over dark fiber, and I am using LD ISL links between switches at each site to create an extended fabric. It's working well.
Except, occasionally we have had some issues with the dark fiber getting noisy, causing the ISL ports to flap on and off. I can see the link fail, loss sync, and loss sig counters going up and up.
The last time this happened, we had some issues due to very long latency as the ports continually tried to re-establish the links. My question is: Is there a way to program the 5300 to automatically disable ports when they exceed some threshold of link stability?
The answer is yes, with Fabricwatch (licensed feature) you can monitor the errors in the ISLs and when a certain error reaches a defined threshold, this feature allows you to automatically disable it (portfence).
besides that, usually a dark fiber does not get noisy occasionally. If you are sure that your SFP's are working fine, you should check with your dark fiber provider. Perhaps a mechanical instability, which leads temporarily to more fiber attenuation...