Guide
Building a Wake-on-LAN magic packet and sending it
Wake-on-LAN lets you switch on a computer that is turned off or asleep by sending its network card a special packet. Home servers, office desktops and lab machines use it constantly. The packet is simple, but sending it takes a program that can emit UDP broadcasts, which a web page cannot do. The page builds the packet exactly and gives you commands for the machines that can send it.
The magic packet
A magic packet contains a synchronisation stream of six bytes, each FF, followed by the target’s 6-byte MAC address repeated sixteen times. That makes 6 + 16 × 6 = 102 bytes. The network card, still powered while the computer is off, scans incoming frames for this pattern and wakes the machine when it sees it. The packet can be the payload of a UDP datagram or a raw Ethernet frame with EtherType 0x0842. UDP to port 9 (the discard port) is the common convention, and port 7 (echo) also appears in tools.
Choosing the destination address
Because the sleeping machine cannot answer ARP, the packet is sent as a broadcast on its own network. Two addresses work: the limited broadcast 255.255.255.255, or the directed broadcast of the subnet, for example 192.168.1.255 for a /24. Enter your network in CIDR form and the page works out the directed broadcast and prints both addresses beside the packet. The sender must be on the same network segment, or on a router that forwards directed broadcasts for that purpose.
SecureOn
Some network cards support an optional password, SecureOn, which is appended to the packet as 4 or 6 bytes. A packet without the correct password is ignored. It is sent in the clear, so it is a convenience against accidents rather than real security. The page accepts the password as hexadecimal and adds it after the MAC repetitions.
Sending it
The page shows the first bytes of the packet and the full hexadecimal, a download of the packet as a .bin file, and a block of commands. For Linux, wakeonlan 00:1a:2b:3c:4d:5e or sudo etherwake -i eth0 00:1a:2b:3c:4d:5e do it with the right packages installed. For Windows, a PowerShell script builds the same bytes and sends them through a UdpClient. Run the commands on a computer in the same network as the target.
A worked example
For the MAC address 00:1a:2b:3c:4d:5e on 192.168.1.0/24, the page reports a 102-byte packet that starts ff ff ff ff ff ff 00 1a 2b 3c 4d 5e and repeats 00 1a 2b 3c 4d 5e sixteen times. It recommends sending it to UDP port 9 (or 7) at 192.168.1.255, or at 255.255.255.255, and shows the Linux and PowerShell commands that do so.
Limits
Both the firmware and the operating system must allow waking from the network, and the machine must stay connected to power. Wake-on-LAN from the Internet needs extra infrastructure, such as a VPN into the network or a always-on helper device. Wi-Fi wake (WoWLAN) works only on some hardware. The page cannot test whether the target woke up. To identify the right MAC address, the MAC Address Lookup tells you the vendor of a card.
Related tools
- MAC Address Formatter converts the address into the style your tool expects.
- MAC Address Lookup checks which vendor a network card comes from.
- Subnet Calculator finds the directed broadcast address of your network.
- Port Number Lookup shows what UDP ports 7 and 9 are assigned to.
Checked against the current version of the Wake-on-LAN Generator on .