Linux – Wake On Lan doesn’t work after some time, how to solve this

linuxnetworkingwake-on-lan

Last week I installed Ubuntu and tried to get it to boot with Wake On Lan.

I rerouted all incoming packets at port 9 to the server. When it's the magic packet the server will boot. All went well until I tried it the next day from a different location. It wouldn't work. So I started Googling and did some tests and found out the server won't respond to the magic packet after x amount of minutes.

I've got telnet access to my router, if there is anything I need changed there.

Best Answer

If your router is configured to forward the WOL packet to your sleeping computer, it needs to be able to discover the computer's MAC address based on the IP address, which is what the ARP protocol does. However, with the computer off, ARP won't work, so once the router's ARP cache becomes stale the relevant entry is removed and you're out of luck (that apparently takes 20 minutes in your case).

Some routers let you configure this ARP mapping statically, or use the static IP configuration as an ARP mapping as well, or contain their own WOL tool to do the job (e.g. Tomato and DD-WRT firmwares) - you'll have to check yours to see if it's supported.

Another option is to forward the WOL packet to the broadcast address (such as 192.168.1.256, if that's your subnet's address), but this too is not supported on all routers.

Related Solutions

Linux – How to get ethtool wake-on-lan setting to “stick”

You could use /etc/rc.local or some system boot scripts, but this wouldn't be the best way to do it. On startup your network interfaces are configured, sure, but there are other times when your network interfaces may be brought up or down and you will need this executed during those times.

You want to edit /etc/network/interfaces:

You should have a line like:

iface eth0 inet static

Underneath that, indented further, you want to create a post-up and post-down commands e.g.

iface eth0 inet static
    post-up /usr/sbin/ethtool -s eth0 wol g
    post-down /usr/sbin/ethtool -s eth0 wol g

Obviously, replace eth0 with the relevant interface if different.

See interfaces(5) for more information on post-up and post-down commands

man 5 interfaces

Wifi – How to boot up Windows Server 2003 remotely using Wake On LAN

1) Wake up on LAN is a feature of the BIOS and network card:

Wake-on-LAN support is implemented on the motherboard (BIOS) of a computer and the network interface (firmware), and is consequently not dependent on the operating system (and NIC drivers) running on the hardware, although the operating system can sometimes control the Wake-on-LAN behaviour.

Source

2) The connection type of the machine sending the wake up signal shouldn't matter. As long as it is fully connected to the network they should be able to send the signal.

In case the computer being woken is communicating via Wi-Fi, the wake-up-packet can be sent via Wireless Multimedia Extensions (WMM)

3) There are tools to help you do this, though configuring the Server should just be a matter of setting up the BIOS correctly. The wake up is done by what Wikipedia calls a "Magic Packet" that contains the IP address of the server to be woken and the "wake-up" packet. This can be sent by any script/program that can access the network:

wolcmd 001122334455 10.0.0.2 255.255.255.255 7

(from the same Wikipedia page).

4) WOL does work over the Internet.

Best Answer

Related Solutions

Linux – How to get ethtool wake-on-lan setting to “stick”

Wifi – How to boot up Windows Server 2003 remotely using Wake On LAN

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