Unicast

More secure solution than subnet-directed broadcasts because the packet is sent directly to a computer rather than to all computers on a subnet.

Does not require reconfiguration of routers.

Consumes less network bandwidth than subnet-directed broadcast transmissions.

Supported with IPv4 and IPv6.

Wake-up packets will fail to find target computers that have changed their subnet address since the last hardware inventory schedule.

Switches might need to be configured to forward UDP packets.

Some network adapters might not respond to wake-up packets in all sleep states when using unicast as the transmission method.

Subnet-Directed Broadcast

Higher success rate than unicast if you have computers that frequently change their IP address within the same subnet.

No switch reconfiguration is required.

High compatibility rate with computer adapters for all sleep states, because subnet-directed broadcasts were the original transmission method for sending wake-up packets.

Less secure solution than using unicast because an attacker could send continuous streams of ICMP echo requests from a falsified source address to the directed broadcast address, causing all of the hosts to reply to that source address. This type of denial of service attack is commonly called a smurf attack and is usually mitigated by not allowing subnet-directed broadcasts If routers are configured to allow subnet-directed broadcasts, the additional configuration is recommended for security reasons:

• Routers should be configured to allow only IP-directed broadcasts from the Configuration Manager site server, using a specified UDP port number.
  
  
• Configuration Manager 2007 must be configured to use the specified non-default port number.
  
  

Might require reconfiguration of all intervening routers to enable subnet-directed broadcasts.

Consumes more network bandwidth than unicast transmissions.

Supported with IPv4 only; IPv6 is not supported.