A 10-gigabit network link between two datacenter racks went offline; the monitoring system showed the link status down. The link joins a storage array to the main virtualization cluster, and it had to be restored quickly lest data access errors follow.

I inspected the network switch ports at both ends of the link and found the port indicators dark. A light meter measured the optical power and showed no signal at one end of the cable. I cleaned the fiber optic cable connectors and measured again; the signal was still zero, which told of a hardware failure. I removed the small form-factor pluggable (SFP+) transceiver from the switch and seated a new, tested SFP+ transceiver in its place.

The port indicator turned green at once, and the network switch logs showed the link up. I verified that the virtualization cluster could speak with the storage array, and the connection held stable. The failure I recorded, and the bad transceiver went back to the manufacturer for analysis.