Link (GBICs) Flapping on one side but not on the other side

[Victor Fabian]

I have a switch that is connected through a fiber connection to the CORE and i am able to see that the flapping happens on the CORE but not on the switch .

How can i determine which one should be replace?

Thank you

Vic

[danrya]

I would try some "show controller giga" commands on both sides and look for errors.

Also, you can switch the transmit and receive on both ends (in other words, unplug side A, and plug the transmit in to receive and vise versa, then do the same to side B). If the flapping moves from the core to the other side, then it's a bad strand of fiber. If not, then you'll have to swap the GBIC's one at a time.