Wednesday, July 25, 2018

Going from 10Gbit to 40Gbit

I'm using Lenovo / IBM G8264 switches. I have a LC fiber connection between buildings - Probably around 1000 feet. We had been using SFP+ 10Gbit with LC connections and "single mode" fiber.

We wanted to test 40Gbit so got some Fiber Store 40Gbit QSFP+ adapters and copied the switch VLAN configs from the 10Gbit port to the 40Gbit port. Plugged it in and it seemed to work.

Overnight, we started having issues with the port going up and down on its own. It would go down every so often, ending up flapping every 10 minutes or so.

We found a LOT of FCS errors on Switch A, but not on Switch B.

We decided to swap the QSFP+ adater on Switch A with a spare. Everything seemed like yesterday with the initial switch - all good. This time however, we checked the FCS error counters, and after a couple minutes they started ticking up again on Switch A. However, 3 hours and no port down event... Will see what happens tomorrow.

Anyway - does any of this lead to additional troubleshooting steps? I was thinking if we do start having the port go down again, we just move the QSFP+ adapter on Switch A to a new Switch port. But I'm also wondering if the fiber might just not handle 40Gbit?



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