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How-To Geek Explains: What is Wake-on-LAN and How Do I Enable It?

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Technology often yields ridiculous conveniences, like being able to turn on your computer from miles away without pushing the power button. Wake-on-LAN, has been around for a while, so let’s see how it works and how we can enable it.

What is Wake-on-LAN?

Wake-on-LAN is an industry standard protocol for waking computers up from a very low power mode remotely. The definition of “low power mode” has changed a bit over time, but we can take it to mean while the computer is “off” and has access to a power source. The protocol also allows for a supplementary Wake-on-Wireless-LAN ability as well.

 

WoL is dependent on two things: your motherboard and your network card. Your motherboard must be hooked up to an ATX-compatible power supply, as most computers in the past decade or so are. Your Ethernet or wireless card must also support this functionality. Because it is set either through the BIOS or through your NIC’s firmware, you don’t need specific software to enable it. Support for WoL is pretty universal nowadays, even when it’s not advertised as a feature, so if you have a computer built in the past decade or so you’re covered. If, however, you have a more modern computer, you may find that you have advanced BIOS options for allowing the computer to power on via a time schedule. It’s not technically WoL, but in terms of functionality, it’s pretty close.

For those of you who build your own rigs, take care when buying an Ethernet card. While most built-in cards on motherboards don’t need this step, discrete network cards often need a 3-pin cable attached to the motherboard to support WoL. Do your research online before you buy so you’re not disappointed later on down the line.

The MagicPacket: How WoL Works

WoL-enabled computers essentially wait for a “magic packet” to arrive that includes the NIC’s MAC address in it. These magic packets are sent out by professional software made for any platform, but can also be sent by routers and internet-based websites. The typical ports used for WoL magic packets are UDP 7 and 9. Because your computer is actively listening for a packet, some power is feeding your network card which will result in your laptop’s battery draining faster, so road warriors should take care to turn this off when you need to eke out some extra juice.

magic packet

Magic packets are usually sent over the entirety of a network and contain the subnet information, network broadcast address, and the MAC address of the target computer’s network card, whether Ethernet or wireless. The above image shows the results of a packet sniffer tool used on magic packet, which brings into question exactly how secure they are when used in unsafe networks and over the internet. On a secure network, or for basic home use, there shouldn’t be any practical reason to worry. Many motherboard manufacturers often implement software along with WoL capabilities to offer hassle-free or largely configuration-free usage scenarios.

Enabling WoL on Your System

BIOS

Most older computers and many modern ones have their WoL settings buried in the BIOS. Depending on your system, you need to hit Escape, F2, or Delete to get into the BIOS, but if you’re not sure then you should check your system’s documentation. Once you’re in, check under Power Management or Advanced Options or something of that sort.

bios

On this HP computer’s BIOS, the setting is found near the “resume after power failure” option.

Many computer, however, do not have a BIOS option. Fortunately, this doesn’t mean that the capability isn’t there, it just means we need to go through the operating system to enable WoL.

Windows

Click Start, then search for and open the Device Manager. Find your networking device in the list.

win1

Right click on it and go to Properties, then click on the Advanced tab.

win2

Scroll down in the list to find “Wake on Magic Packet” and change the Value to “Enabled.” You can leave the other “Wake on” settings alone. Click OK when you’re done.

OS X

Open up your System Settings and choose Energy Saver.

energysaver

Under the Options tab, you should see “Wake for Ethernet” or something similar. This enables Wake-on-LAN.

Linux

Ubuntu has a great tool that can check to see if your machine supports WoL and can enable it. Open up a terminal and install “ethtool” with the following command:

sudo apt-get install ethtool

You can check your compatibility by running:

sudo ethtool eth0

If your default interface is something else, substitute it for “eth0”.

wol ubuntu

Look for the “Supports Wake-on” section. As long as one of the letters listed is “g,” you can use magic packets for WoL. To enable this option, use the following command.

sudo ethtool -s eth0 wol g

This should take of it. You can run the command to check and see if it’s enabled now. Look for the “Wake on” section. You should see a “g” instead of a “d” now.

wol ubuntu 2

Sending WoL Magic Packets

To send out WoL requests, you have a cornucopia of options available.

depicus

Depicus has an excellent series of lightweight tools to get the job done, including a GUI-based one for Windows and command-line-based one for both Windows and Mac OS. Wiki.tcl.tk has a great cross-platform lightweight script that handles the requests as well.

DD-WRT has great WoL support, so if you don’t feel like downloading software to do it, you really don’t have to. Lastly, if you’re out and about, you can use your Android device to wake your computers.


What software do you use to manage and send Wake-on-LAN requests? Do you know of an easier way to enable WoL support? Tell us what you know in the comments!

 

Yatri Trivedi is a monk-like geek. When he's not overdosing on meditation and geek news of all kinds, he's hacking and tweaking something, often while mumbling in 4 or 5 other languages.

  • Published 08/12/11

Comments (14)

  1. do you want to play a game?

    Good, interesting article. Thanks.

    Does the UEFI also have this feature?

  2. Xantes

    WOL is not a feature dependent of the Operating System’s NIC’s settings! It’s only dependent of the BIOS’ settings!
    Consequently you can wake a computer leaving the computer’s NIC with its default settings!
    And to check that what I am saying is true do the right WOL settings in your PC’s BIOS and then remove your hard drive from your computer – where actually the NOC’s settings reside – and try to WOL that PC and you’ll be surprised to see that can boot up only by BIOS settings!
    For instance my laptop has such a BIOS that comes by default with WOL settings activated and there is no way to switch off this feature! It’s just not there! Nothing to turn on or off!
    On my desktop computer WOL settings must be activated from its BIOS but there is no need – like I said – to set anything from the NIC’s interface within its operating system!

  3. John

    I use WOL on my work PC. It works great if you actually remember you have it set up. I was at a trade show recently and the power flickered back at my office. (It was just short enough that it didn’t power back on automatically.) Anyhow, I totally forgot I had it set up and called someone to stop by the office and start my PC. I guess that the poor man’s WOL.

  4. Mike

    What’s the most common use for this?
    Does the machine just power on and stop at the login screen?

  5. Keith

    The most common use for Wake-on-Lan (“WoL”) would be:

    1) A corporate setting where users commonly turn off their computers when they leave for the day but administrators need to do updates at night remotely or,

    2) Someone wants to be as environmentally friendly so they turn off their home computer when they leave but know they will have to access it remotely.

    Any other uses anyone can think of?

    Keith

  6. Keith

    Additional note for Cisco E4200 routers and Wake-on-Lan:

    If you have firmware v1.0.0.2 (the latest as of this posting), don’t bother trying. Wake-on-Lan over LAN works just fine with this router and the above-mentioned firmware. Wake-on-Lan over WAN (internet), however, does not. That functionality was broken with this firmware and Cisco’s users forums support my conclusion. I’ve tried work-around after work-around after work-around to no avail (and a “work-around” shouldn’t really be necessary)

    In order to get WoL over WAN to function with this router, you’ll have to download and burn v1.0.0.1 or wait for firmware v1.0.0.3. Alternately, you can burn alternate firmware such as Tomato or DD-WRT, as suggested above.

    Keith

  7. Edward Allen Weissbard

    Interesting note Keith. I did have v1.0.0.2 but “upgraded” to DD-WRT, I have yet to try WAN WOL yet, though.

  8. Xantes

    WOL is not a feature dependent of the Operating System’s NIC’s settings! It’s only dependent of the BIOS’ settings!
    Consequently you can wake a computer leaving the computer’s NIC with its default settings!
    And to check that what I am saying is true do the right WOL settings in your PC’s BIOS and then remove your hard drive from your computer – where actually the NOC’s settings reside – and try to WOL that PC and you’ll be surprised to see that can boot up only by BIOS settings!
    For instance my laptop has such a BIOS that comes by default with WOL settings activated and there is no way to switch off this feature! It’s just not there! Nothing to turn on or off!
    On my desktop computer WOL settings must be activated from its BIOS but there is no need – like I said – to set anything from the NIC’s interface within its operating system!!!

  9. astral_cyborg

    Nice article, as always. Thank you for the useful information.

  10. Keith

    I neglected to answer Mike’s question above about what happens when WoL is activated. “Does it just sit there at the logon screen?”, he asked? Yes, it does. It’s just as if you pressed the power button.

    At that point, perhaps you may have a VPN that you need to access? Perhaps an FTP server on the computer? But now, your computer is on.

    From there, you can also use Windows Remote Access or additional software to remotely control your computer (LogMeIn and TightVNC come to mind, but there are certainly others).

    Note/trivia: You’ll see “VNC” mentioned quite often. VNC stands for Virtual Network Computing, and it is a PROTOCOL, not a program. It’s secure and old enough to be trusted and reliable. Do not confuse VNC, the protocol, with any product that may use VNC in their product name.

  11. Tyler

    I have a web server with which I would like to use this (in case, for example, I’m out of town and there’s a storm which interrupts power). It is a fairly old computer (a little over ten years years is my best guess — it’s an HP Pavillion XT983, and I couldn’t find too much information about it) which runs Ubuntu Server 11.04. I ssh’d into the root account, installed and ran ethtool, and got Supports Wake-On: pumbg and Wake-On: d, after which I ran the command to enable it, ran ethtool again, and got Supports Wake-On: pumbg and Wake-On: g. I powered the server down, and using several methods, was not able to wake it. I restarted it manually, ran ethtool again, and found Wake-On was back to being listed as d. I tried the process over with the same result. Do I have to do something else? I tried this on my primary computer (running Ubuntu 11.04), same thing only Supports Wake-On listed only g, and it worked.

  12. Xantes

    WOL is not a feature dependent of the Operating System’s NIC’s settings! It’s only dependent of the BIOS’ settings!
    Consequently you can wake a computer leaving the computer’s NIC with its default settings!
    And to check that what I am saying is true do the right WOL settings in your PC’s BIOS and then remove your hard drive from your computer – where actually the NOC’s settings reside – and try to WOL that PC and you’ll be surprised to see that can boot up only by BIOS settings!
    For instance my laptop has such a BIOS that comes by default with WOL settings activated and there is no way to switch off this feature! It’s just not there! Nothing to turn on or off!
    On my desktop computer WOL settings must be activated from its BIOS but there is no need – like I said – to set anything from the NIC’s interface within its operating system!!!!

  13. Xantes

    WOL is not a feature dependent of the Operating System’s NIC’s settings! It’s only dependent of the BIOS’ settings!
    Consequently you can wake a computer leaving the computer’s NIC with its default settings!
    And to check that what I am saying is true do the right WOL settings in your PC’s BIOS and then remove your hard drive from your computer – where actually the NOC’s settings reside – and try to WOL that PC and you’ll be surprised to see that can boot up only by BIOS settings!
    For instance my laptop has such a BIOS that comes by default with WOL settings activated and there is no way to switch off this feature! It’s just not there! Nothing to turn on or off!
    On my desktop computer WOL settings must be activated from its BIOS but there is no need – like I said – to set anything from the NIC’s interface within its operating system!

    P.S. I’ll keep sending my comment until you’ll post it! Every single day!

  14. Xantes

    WOL is not a feature dependent of the Operating System’s NIC’s settings! It’s only dependent of the BIOS’ settings!
    Consequently you can wake a computer leaving the computer’s NIC with its default settings!
    And to check that what I am saying is true do the right WOL settings in your PC’s BIOS and then remove your hard drive from your computer – where actually the NIC’s settings reside – and try to WOL that PC and you’ll be surprised to see that can boot up only by BIOS settings!
    For instance my laptop has such a BIOS that comes by default with WOL settings activated and there is no way to switch off this feature! It’s just not there! Nothing to turn on or off!
    On my desktop computer WOL settings must be activated from its BIOS but there is no need – like I said – to set anything from the NIC’s interface within its operating system!

    I’ll keep sending my comment until you’ll post it! Every single day!

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