Wake on LAN - Knowledge Base

1. Wake on LAN does not boot all the machines.

Check the following:

On the Machine

1. NIC should be wake on LAN complaint
2. In BIOS WOL should be enabled
3. Most external NIC's will have 3 PIN WOL cable which has to be connected to the motherboard.
4. You can see a blinking light in the NIC even if the machine is powered off.
5. Ensure that the power supply to the machine is switched ON.

On the Network

For Wake On LAN to work across subnets (or VLANs)

1. Enable IP Directed broadcasts on the routers/gateways. This ensures that the WOL packets are not blocked.
2. IP directed broadcasts has to be enabled in all the required routers/gateways/switches along the path. This depends on the network design.
3. Alternatively, you can also add an access list in the switches to allow UDP packets from a specific machine to other subnets. For example: Access-list 101 permit udp 192.168.110.103 host 192.168.116.255 eq 5000, where
   
   192.168.110.103 - refers to the machine generating the WOL packets
   
   192.168.116.255 - refers to broadcast address that is being permitted
   
   5000 - refers to the port from which the WOL packet is being sent from the generating machine.
   
   This again needs to be enabled in all the routers/switches along the path

Questions