Computer Waking up on Ping
Posted on 2008-10-24
I often use Wake on LAN (WoL) to remotely switch on my home PC via one of my home servers.
However, I seem to have a problem in that while I wait for my PC to boot up, I'll start a continuous ping from the server to my PC using the -t switch, to determine when the PC is awake and ready to roll. Occasionally I'll forget to close this ping, which has the surprising effect when I shut down my PC of it instantly starting it back up again - just like I had sent a WoL packet.
1. Firstly, why does this occur? I thought WoL uses UDP packets and transmits based on MAC address; how can a ping - based upon IP address - work when the PC is off. Just as a note, the ping does reply with a Request Time Out message, so the ping isn't being returned, but something is picking it up and starting my PC up based upon it.
2. Secondly, is there a way to prevent this behaviour? Yes, I should just close the ping window, but suppose someone else decided to ping my computer or do a scan of the entire IP subnet, my PC would wake up.
I know it is the ping - if I pull the network cable, or indeed close the ping, the PC will stop starting up as a result.