Using Wake-on-LAN with AnyDesk and AnyClassroom

Technical Guide for IT Directors and Lab Administrators

Remote access to university labs 24/7 is one of the greatest benefits of AnyClassroom. Modern equipment in sleep mode already consumes very little power, and in that state there is no need to use Wake-on-LAN. However, Wake-on-LAN (WoL) represents an opportunity to save even more energy by allowing computers to be completely powered off when not in use, turning them on only when needed. It is a complementary tool to further optimize the energy management of your infrastructure.

That said, WoL is not a magic or infallible solution. This guide explains what it is, how to configure it correctly with AnyDesk and AnyClassroom, its energy advantages, and —most importantly— its limitations and when it is preferable to opt for more robust alternatives.

What is Wake-on-LAN

Wake-on-LAN is a network standard that allows you to turn on a powered-off computer by sending a special data packet called a magic packet over the local network. The magic packet is a broadcast frame containing a specific sequence of 6 bytes of value 0xFF followed by 16 repetitions of the MAC address of the target computer’s network card.

When the computer’s network card receives this packet, it sends a signal to the motherboard that initiates the boot process. The computer turns on without anyone having to physically press the power button.

How WoL Works with AnyDesk

AnyDesk includes native functionality to send WoL magic packets. The flow is as follows:

1. One computer on the local network stays powered on with AnyDesk active. This computer acts as a WoL “relay” or repeater.
2. From the AnyDesk interface (local or remote), the administrator requests to turn on a powered-off computer.
3. AnyDesk sends the magic packet through the relay computer to the MAC address of the target computer.
4. The target computer turns on and AnyDesk starts automatically, allowing remote connection.
5. AnyClassroom can then assign that computer to a student who has reserved it.

Energy Advantages of WoL

Modern processors and peripherals are remarkably efficient. A current lab computer in sleep mode (S3) consumes between 1W and 3W —very little compared to previous generations. By properly configuring low-power modes and automatic screen shutoff, significant energy savings are already achieved without needing WoL.

Wake-on-LAN is an extreme savings option that allows going one step further: from 1-3W (sleep mode) to 0.5-1.5W (complete shutdown with network card standby). While the savings per computer are small, in a lab with 40-60 computers running 24/7 for 365 days, that difference adds up:

• Marginal savings per computer: 0.5-1.5W additional when going from sleep to complete shutdown. In a 50-computer lab, this represents 25-75W constant.
• Estimated annual savings: A 50-computer lab going from permanent sleep mode to complete shutdown with WoL can save between $200 and $600 USD annually in additional electricity costs, depending on local rates.
• Carbon footprint: Each constant watt represents approximately 8.7 kg of CO₂ per year. Reducing 50W constant is equivalent to avoiding ~435 kg of CO₂ emissions annually.
• Thermal and ventilation: Fewer computers in sleep means less residual heat, marginally reducing the load on the lab’s climate control system.
• Hardware lifespan: Completely powering off computers reduces wear on power supplies, fans, and drives, compared to keeping them in sleep indefinitely.

It is important to note that the greatest energy savings come from properly configuring low-power modes and screen shutoff, not from WoL. WoL is the final optimization layer for institutions looking to maximize savings down to the last watt.

Requirements for Implementing WoL

Wake-on-LAN requires three simultaneous conditions: BIOS/UEFI configuration, network configuration, and availability of a relay device on the local network.

1. BIOS/UEFI Configuration

Each lab computer must have WoL enabled in its BIOS/UEFI:

• Enable Wake-on-LAN: The option is usually in the power or network configuration menu of the BIOS. The name varies by manufacturer: “Wake on LAN”, “Power On by PCI-E”, “Wake on PCI Event”, “Resume by Onboard LAN”, among others.
• Disable Fast Boot / Quick Boot: Fast boot can interfere with network card initialization. It should be disabled to ensure the network card is ready to receive the magic packet.
• ACPI power configuration: The sleep state must allow the network card to maintain power. In some BIOSes, this is called “ErP Ready” and should be set to “Enable” or “S4+S5” mode.
• BIOS updates: On older computers, it may be necessary to update the BIOS to resolve known WoL implementation bugs.

2. Network Configuration

The network infrastructure must allow the magic packet to pass through:

• Network card with WoL support: Virtually all modern integrated network cards (Intel, Realtek, Broadcom) support WoL. USB network cards generally do not.
• Configured network driver: In the operating system, the network card driver must have the “Wake on Magic Packet” option enabled (Windows) or the equivalent in Linux (ethtool -s eth0 wol g).
• Switches and routers: The magic packet is a broadcast frame. Switches must allow broadcast on the lab VLAN. If there is network segmentation, the magic packet does not cross VLANs by default — additional configuration is required (IP directed broadcast or WoL relay).
• Windows Fast Startup: In Windows 10/11, the “Fast Startup” feature can interfere with WoL. It should be disabled from Control Panel > Power Options > Choose what the power buttons do.
• ARP and switching tables: On large networks, switch ARP tables can forget the MAC address of the powered-off computer after a few minutes. This prevents the magic packet from reaching its destination. Solution: configure static ARP entries or use IP-directed WoL.

3. Relay Device with AnyDesk on the Network

WoL only works within the same local network (Layer 2). To turn on a computer from outside the campus, you need:

• At least one powered-on computer on the same lab network with AnyDesk active and remotely accessible.
• AnyDesk configured with WoL functionality enabled and the MAC addresses of the lab computers registered.
• This relay computer must always be available. If the only relay computer is turned off or loses connection, it will not be possible to remotely turn on the rest of the lab.

The Reality of WoL — Limitations and Critical Considerations

It is fundamental to understand that Wake-on-LAN does not depend solely on AnyDesk. AnyDesk is simply the vehicle for sending the magic packet. WoL reliability depends on the stability and consistency of BIOS and network configurations of each computer.

Real Problems in Lab Environments

In practice, university lab IT administrators face the following problems with WoL:

• Inconsistency between manufacturers: Each motherboard manufacturer implements WoL slightly differently. A lab with computers from different brands and models requires individual BIOS configuration for each one.
• BIOS updates that reset config: A BIOS update or CMOS reset can silently disable WoL. The computer will stop turning on remotely without anyone noticing until someone tries to use it.
• Network drivers that update: Automatic Windows updates can change the network driver configuration and disable “Wake on Magic Packet”.
• Windows Fast Startup: After a Windows update, the fast startup feature may re-enable itself, breaking WoL.
• Switches that age ARP tables: On networks with many computers, the switch can forget the MAC of the powered-off computer in 5-15 minutes, making it impossible to send the magic packet.
• Computers that hibernate vs shut down: WoL works from S3 (sleep) and S5 (complete shutdown) states, but not from deep hibernation on some hardware.
• Incompatible power supplies: Some low-wattage power supplies do not maintain sufficient auxiliary power (5V standby) for the network card when the computer is powered off.

When WoL Is Not the Best Option

Since modern computers in sleep mode already consume very little power (1-3W), the additional savings from WoL is marginal. In environments where availability is critical —for example, labs that must be immediately accessible for exams, thesis defenses, or ongoing research— the fragility of WoL can be a bigger problem than the energy savings it provides.

In these cases, it is preferable to configure low-power modes and screen shutoff, which already offer an excellent balance between energy savings and immediate availability:

• Sleep mode (S3): The computer consumes between 1W and 3W, maintains the active session, and wakes up in seconds via AnyDesk. Does not require WoL.
• Screen off with computer active: The computer continues running but the screen turns off after 5-10 minutes of inactivity. AnyDesk can connect at any time. The screen represents 30-50% of the total visible consumption.
• CPU low-power modes: Configure the operating system to reduce CPU frequency and spin down unused drives after inactivity. The computer remains accessible but consumes less.
• Scheduled shutdown policies: Automatically shut down computers at a fixed time (e.g., 2:00 AM) and turn them on before the first class period (e.g., 6:00 AM) using a scheduled task or network script, instead of relying on on-demand WoL.

Comparison — WoL vs Low-Power Modes

Recommendation for Labs with AnyClassroom

For institutions using AnyClassroom, the ideal energy strategy is hybrid and policy-based:

Step 1 — Optimize low-power modes (always)

Before considering WoL, ensure all lab computers are configured with:

• Automatic screen shutoff after 5-10 minutes of inactivity.
• Sleep mode (S3) after 15-30 minutes of inactivity.
• CPU frequency reduction and drive spin-down when idle.
• This alone reduces consumption from full load to 1-3W per computer in sleep.

Step 2 — WoL for extreme savings on non-critical computers

Building on the above, WoL allows completely shutting down computers and turning them on on demand:

• General-use labs that do not require immediate availability.
• Computers reserved in advance (the system can turn them on 10 minutes before the reservation).
• Labs outside teaching hours (nights, weekends).

Step 3 — Keep sleep mode on critical computers

• Labs used for exams or thesis defenses.
• Research computers that must be accessible 24/7.
• Labs with continuous schedules where a student may reserve with little notice.

Practical Implementation

1. Inventory computers: Document brand, model, MAC address, and WoL compatibility of each lab computer.
2. Standardize BIOS: Create a BIOS configuration template per manufacturer and apply it centrally (Dell Command, HP BIOS Configuration Utility, or custom scripts).
3. Configure AnyDesk: Register the MAC addresses of all computers in AnyDesk for WoL.
4. Designate relay computers: Ensure at least 2 lab computers remain always powered on as WoL relays (redundancy).
5. Monitor: Implement a monitoring script that weekly verifies WoL works on each computer, and alerts if any does not respond.
6. Plan B: For computers where WoL repeatedly fails, keep sleep mode with screen off as a fallback.

Conclusion

Modern computers are already very energy efficient. By properly configuring low-power modes and automatic screen shutoff, most of the possible energy savings are achieved without needing WoL. Wake-on-LAN is an extreme optimization option that allows completely shutting down computers and turning them on on demand, saving those last additional watts.

However, WoL is not a universal solution. Its reliability depends on multiple factors —BIOS, network, drivers, hardware— that can change without warning and break the configuration. The key is to evaluate the level of availability required for each lab. For environments where availability is critical, low-power modes with screen off offer a more robust and predictable alternative, with only slightly higher energy consumption.

The ideal strategy combines both approaches: low-power modes as a baseline, and WoL as an additional extreme savings layer for non-critical computers. Whatever strategy is chosen, AnyClassroom manages student access to computers transparently, regardless of whether the computer was in sleep or turned on on demand.