I have been trying for 2 days to troubleshoot a fiber connection that I need between an existing Arista and a Cisco 3650. Right now, I can't get a lot of equipment to connect all with SFP-LH-SMD transceivers. This is a high-level summary of the situation, but it's really strange (and YES, I have swapped the transmit and receive).
This single mode connection is ran through multiple closets in the same building. I need 5 patch cables for 1 connection, but it is definitely not near the max length. Our cabling company tested the 2 connections that I need, found an issue with one, but we moved it to a different cable run. The fiber can't be the issue.
This is what I was seeing on the switches. I was seeing one switch link flap and err-disable every time at first, and now I'm not getting anything. I did a lot of "show interface transceiver" commands. It looked like 1 strand was good and 1 was bad in both directions, but I couldn't get a link. I put an old 3560 with the same SFP in one of the closets in the middle, and it could connect to the Arista and to the 3650.
Next, I brought the 3650 to that closet, wiped the config to make sure nothing was causing problems, configured a trunk, and I started not getting a link at all. However, a "show interface transceiver" looked great. I even plugged the 3650 directly to a 5k in that closet, and it was identical. I can't even get a connection to come up between the 3560 and the 5k (taking the 3650 completely out of the equation). I even tried some GLC-T SFPs between the 5k and the 3560, and still couldn't get a link. I wasn't using a crossover cable, but I would assume that the 5k can automatically.
I brought in a couple coworkers, and I don't see any reasons why this should happen unless we are frying SFPs or we are missing something very obvious.
My questions:
Has anyone worked with an Arista and the SFP-LH-SMD transceivers?
Has anyone seen a link flap like this one even with multiple cable runs and fiber that has been tested?
What would cause 2 trunks to not at least go UP/DOWN when there is light going to both switches?
Does anyone have any other ideas?
Here's some more info:
3650 is running IOS-XE 3.7.5.
The Aristas are old (don't have the model # right now), but are working with other Cisco SFPs.
The Aristas are in an area in which I have to jump through hoops to access.
I passed my CCNP switch, and I've been doing this for a while.
Thanks!
