Computer Waking up on Ping
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.
Any ideas?
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.
Any ideas?
ASKER
Thanks for that Werrock. Could you just explain in a little more detail how:
1. this would cause my PC to wake up when I am pinging it?
2. What protocol does WoL use. UDP / ICMP? I have no idea when it comes to WoL except on the basis of using it...
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If its a linux server you will need to set the NIC to wake on only magic packets.
ethtool eth0
this will give some output
to set to magic packet only enter:
ethtool -s eth0 wol g
http://linuxcommand.org/man_pages/ethtool8.html
ethtool eth0
this will give some output
to set to magic packet only enter:
ethtool -s eth0 wol g
http://linuxcommand.org/man_pages/ethtool8.html
ASKER
Thanks for that, Windows XP sadly :-)
Maybe if you could get ping to always use an ARP before each ICMP request it could work. But I do not know how to do this. Hopefully someone else can solve that part.