Today I wanted to copy some documents to my Linux file server and couldn’t find it on the network. It was there yesterday! Two desktop clients couldn’t find it either by IP address or hostname. My smartphone couldn’t locate it. The internet was working on all the computers including the server. The server was checked and I found it running and the uptime command indicated it has been up for many days. I power-cycled the network connectivity devices to no avail. Finally, I ran the ip address command at the server and found the ethernet address had changed. No wonder my computer clients couldn’t find it. I checked the network settings still had the old, desired address. I don’t know what happened and I’ll have to investigate later.