Step 6 - Configure port forwarding
Configuring port forwarding on your router is a required change; WOL won't work without it.
WOL uses UDP as its Layer 4 transport, but the port varies based on the utility. The mc-wol.exe utility uses UDP port 65535. AMD's Magic Packet Utility uses UDP port 2304. There is a Linux tool, aptly named wakeonlan, that uses UDP port 9.
An easy way to find the port is to use a packet sniffer utility to see which port is used. Ethereal (now Wireshark) is probably the best known, and a very powerful free download. If you're into networking, it is an invaluable troubleshooting tool. You may find this tool comes in handy if you're using a different WOL utility and need to find the port number.
Figure 6 below is the Wireshark capture of a WOL packet. The areas titled MAC ADDRESS and IP Address are blanked out in the example, because you'll see your own MAC and IP addresses when you run it. The key is the Dst Port (Destination Port). This is what you're looking for.
Figure 6: Wireshark's packet capture showing the destination port
Once you have the port number, you have what you need. You'll need to go into your router's port forwarding menu and set up a rule to forward UDP packets sent to the WOL port to the broadcast IP address of your LAN.
Some routers don't allow broadcast IPs to be used as a target IP. This is where having Static DHCP comes in handy. If you have configured Static DHCP, and your router has the MAC of your target PC, you can configure your router to forward the WOL packet directly to the IP address of the target PC.
Figure 7 below is a screen shot from a Linksys RV042 router. Port forwarding is configured in the Setup menu under the Forwarding tab.
Figure 7: Setting up port forwarding on a Linksys RV042 router
Figure 8 below is a screen shot from a Zyxel P-334WT router with several port forwarding rules configured. Port forwarding is configured in the Network menu under the NAT-Port Forwarding tab.