I’ve had my fair share of issues with Cisco, but my horror story comes from a pair of Dell EMC switches.
During a datacentre migration, the 2 aforementioned switches just would not communicate with each other. They were stacked together using virtual link trunking. There was nothing in the logs to suggest there was a problem, and everything was reported as up.
After nearly 24 hours of panic and scouring nearly every resource I could find, I came across an offhand comment in a reddit post about a certificate. This lead me down a rabbit hole where I eventually found the answer. Turns out the Dell CA certificate had expired and we needed to use a dodgy looking python script to replace the certificate. Boy was I relieved when everything kicked back into life again.
I had the same problem. I ended up filing off a bit on the far edge.