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Equivalent terms include wake on WAN, remote wake-up, power on by LAN, power up by LAN, resume by LAN, resume on LAN and wake up on LAN. If the computer being awakened is communicating via Wi-Fi, a supplementary standard called Wake on Wireless LAN (WoWLAN) must be employed.[1]

Wake on Lan


Ethernet connections, including home and work networks, wireless data networks and the Internet itself, are based on frames sent between computers. WoL is implemented using a specially designed frame called a magic packet, which is sent to all computers in a network, among them the computer to be awakened. The magic packet contains the MAC address of the destination computer, an identifying number built into each network interface card ("NIC") or other ethernet device in a computer, that enables it to be uniquely recognized and addressed on a network. Powered-down or turned off computers capable of Wake-on-LAN will contain network devices able to "listen" to incoming packets in low-power mode while the system is powered down. If a magic packet is received that is directed to the device's MAC address, the NIC signals the computer's power supply or motherboard to initiate system wake-up, in the same way that pressing the power button would do.

Because Wake-on-LAN is built upon broadcast technology, it can generally only be used within the current network subnet. There are some exceptions, though, and Wake-on-LAN can operate across any network in practice, given appropriate configuration and hardware, including remote wake-up across the Internet.

In order for Wake-on-LAN to work, parts of the network interface need to stay on. This consumes a small amount of standby power, much less than normal operating power. The link speed is usually reduced to the lowest possible speed to not waste power (e.g. a Gigabit Ethernet NIC maintains only a 10 Mbit/s link). Disabling wake-on-LAN when not needed can very slightly reduce power consumption on computers that are switched off but still plugged into a power socket.[5] The power drain becomes a consideration on battery powered devices such as laptops as this can deplete the battery even when the device is completely shut down.

Wake-on-LAN can be a difficult technology to implement, because it requires appropriate BIOS/UEFI, network card and, sometimes, operating system and router support to function reliably. In some cases, hardware may wake from one low power state but not from others. This means that due to hardware issues the computer may be waking up from the "soft off state" (S5) but doesn't wake from sleep or hibernation or vice versa. Also, it is not always clear what kind of magic packet a NIC expects to see.

Certain NICs support a security feature called "SecureOn". It allows users to store within the NIC a hexadecimal password of 6 bytes. Clients have to append this password to the magic packet. The NIC wakes the system only if the MAC address and password are correct. This security measure significantly decreases the risk of successful brute force attacks, by increasing the search space by 48 bits (6 bytes), up to 296 combinations if the MAC address is entirely unknown. However any network eavesdropping will expose the cleartext password. Still, only a few NIC and router manufacturers support such security features.[citation needed]

IT shops using Wake-on-LAN through the Intel AMT implementation can wake an AMT PC over network environments that require TLS-based security, such as IEEE 802.1X, Cisco Self Defending Network (SDN), and Microsoft Network Access Protection (NAP) environments.[15] The Intel implementation also works for wireless networks.[15]

The 3-pin WoL interface on the motherboard consist of pin-1 +5V DC (red), pin-2 Ground (black), pin-3 Wake signal (green or yellow).[20] By supplying the pin-3 wake signal with +5V DC the computer will be triggered to power up provided WoL is enabled in the BIOS/UEFI configuration.

If the sender is on the same subnet (local network, aka LAN) as the computer to be awakened there are generally no issues. When sending over the Internet, and in particular where a NAT (Network Address Translator) router, as typically deployed in most homes, is involved, special settings often need to be set. For example, in the router, the computer to be controlled needs to have a dedicated IP address assigned (aka a DHCP reservation). Also, since the controlled computer will be "sleeping" except for some electricity on to part of its LAN card, typically it will not be registered at the router as having an active IP lease.

Most home routers are able to send magic packets to LAN; for example, routers with the DD-WRT, Tomato or PfSense firmware have a built-in Wake-on-LAN client. OpenWrt supports both Linux implementations for WoL etherwake and WoLs.

Newer versions of Microsoft Windows integrate WoL functionality into the Device Manager. This is available in the Power Management tab of each network device's driver properties. For full support of a device's WoL capabilities (such as the ability to wake from an ACPI S5 power off state), installation of the full driver suite from the network device manufacturer may be necessary, rather than the bare driver provided by Microsoft or the computer manufacturer. In most cases[citation needed] correct BIOS/UEFI configuration is also required for WoL to function.

The ability to wake from a hybrid shutdown state (S4) (aka Fast Startup) or a soft powered-off state (S5) is unsupported in Windows 8 and above,[22][23] and Windows Server 2012 and above.[24] This is because of a change in the OS behavior which causes network adapters to be explicitly not armed for WoL when shutdown to these states occurs. WOL from a non-hybrid hibernation state (S4) (i.e. when a user explicitly requests hibernation) or a sleep state (S3) is supported. However, some hardware will enable WoL from states that are unsupported by Windows.[22][23]

The feature is controlled via the OS X System Preferences Energy Saver panel, in the Options tab. Marking the Wake for network access checkbox enables Wake-on-LAN. It can also be configured through the terminal using the pmset womp (wake on magic packet) command.

Since then many options have been added and standards agreed upon. A machine can be in seven power states from S0 (fully on) through S5 (powered down but plugged in) and disconnected from power (G3, Mechanical Off), with names such as "sleep", "standby", and "hibernate". In some reduced-power modes the system state is stored in RAM and the machine can wake up very quickly; in others the state is saved to disk and the motherboard powered down, taking at least several seconds to wake up. The machine can be awakened from a reduced-power state by a variety of signals.

The machine's BIOS/UEFI must be set to allow Wake-on-LAN. To allow wakeup from powered-down state S5, wakeup on PME (Power Management Event) is also required. The Intel adapter allows "Wake on Directed Packet", "Wake on Magic Packet", "Wake on Magic Packet from power off state", and "Wake on Link".[26] Wake on Directed Packet is particularly useful as the machine will automatically come out of standby or hibernation when it is referenced, without the user or application needing to explicitly send a magic packet. Unfortunately in many networks waking on directed packet (any packet with the adapter's MAC address or IP address) or on link is likely to cause wakeup immediately after going to a low-power state. Details for any particular motherboard and network adapter are to be found in the relevant manuals; there is no general method. Knowledge of signals on the network may also be needed to prevent spurious wakening.

If a machine that is not designed to support Wake-on-LAN is left powered down after power failure, it may be possible to set the BIOS/UEFI to start it up automatically on restoration of power, so that it is never left in an unresponsive state. A typical BIOS/UEFI setting is AC back function which may be on, off, or memory. On is the correct setting in this case; memory, which restores the machine to the state it was in when power was lost, may leave a machine which was hibernating in an unwakeable state.

The Wake on LAN (WOL) feature wakes a computer from a low-power state when a network adapter detects a WOL event. Typically, such an event is a specially constructed Ethernet packet. The default behavior in response to WOL events has changed from Windows 7 to Windows 10.

In Windows 10, the default shutdown behavior puts the system into the hybrid shutdown (also known as Fast Startup) state (S4). And all devices are put into D3. In this scenario, WOL from S4 or S5 is unsupported. Network adapters are explicitly not armed for WOL in these cases, because users expect zero power consumption and battery drain in the shutdown state. This behavior removes the possibility of invalid wake-ups when an explicit shutdown is requested. So WOL is supported only from sleep (S3), or when the user explicitly requests to enter hibernate (S4) state in Windows 10. Although the target system power state is the same between hybrid shutdown and hibernates (S4), Windows will only explicitly disable WOL when it's a hybrid shutdown transition, and not during a hibernate transition.

Ever wish you could wake your computer out of sleep mode without trudging over to it and pressing the power button? Wake-on-LAN allows you to turn your computer on using its network connection, so you can start it up from anywhere in the house with the tap of a button.

For example, I often use Chrome Remote Desktop to access my workstation upstairs. But if my workstation is sleeping, I don't need to go upstairs and turn it on. Wake-on-LAN allows me to wake that computer up with a "magic packet" sent from my phone or laptop, so I can remote in without hassle.

On some machines, it will be very clearly labeled in the sleep and wake settings. In other cases, like on my MSI motherboard, it is part of the Resume By PCI-E Device setting. You can see in the screenshot above that this setting's description mentions "integrated LAN controllers," which is exactly what we're looking for. Toggle that setting to Enabled. 041b061a72


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