I wrote instructions for how to configure Wake On Lan forwarding using a Cisco IOS device, this article will focus on how to configure a Cisco ASA firewall.
Wake On LAN is an Ethernet standard that allows for a device to be powered on when receiving a specially crafted “magic packet”. The “magic packet” is a broadcast frame consisting of 6 bytes of 255 (FF FF FF FF FF FF) followed by sixteen repetitions of the 48-bit MAC address. Turned off computers receiving the broadcast don’t actually process the message up the protocol stack, they are just looking out for a matching 102-byte string.
From what I can tell, unlike Cisco IOS the ASA doesn’t support “IP Directed Broadcasts”, likely to prevent Smurf Attacks. However with some clever NAT rules it’s possible to achieve something similar by using NAT to translate the inbound unicast packet and send it on to the broadcast address for your internal subnet.
Continue reading How To – Enable Wake On Lan using a Cisco ASA