CompTIA Network+

Answer: A - The most common cause of loss of connectivity are issues with the physical layer.

Key Takeaway: As engineers, we sometimes tend to look more deeply than we need to. The vast majority of network connectivity issues have to do with a power outage or a cable being unseated. Always check these first! There was a network engineer who went to fix a printer that would not connect to the network. He ran all sorts of analyses on the network, the switch, the print server, and the printer, only to find out that when the client had moved the printer, they had neglected to plug the data cable back in.