About Unicast Wake-Up Packets for Wake On LAN

Aplica-se a: System Center Configuration Manager 2007, System Center Configuration Manager 2007 R2, System Center Configuration Manager 2007 R3, System Center Configuration Manager 2007 SP1, System Center Configuration Manager 2007 SP2

Unicast, as the transmission method for sending wake-up packets to a computer in a Configuration Manager 2007 site, uses the IP address of the target computer from hardware inventory to route to the target computer's subnet, and it uses the Media Access Control (MAC) address of the target computer from hardware inventory to construct the wake-up packet. When the wake-up transmission reaches the target computer's subnet, the wake-up packet is sent directly to the target computer.

If the target computer has changed its IP address since it last sent its inventory information, the wake-up packet will reach the wrong computer but it will not wake it up because the MAC address in the wake-up packet transmission will not match.

If you have computers that move between subnets, you might be able to reduce the likelihood of failed wake-up transmissions by increasing the Dynamic Host Configuration Protocol (DHCP) lease time and configuring the hardware inventory schedule to run more frequently.

One of the benefits of using unicast to send wake-up packets is that you rarely have to reconfigure the network infrastructure. However, one possible exception to this is the following:

  • Switches must forward UDP packets, and not all switches are configured to do so by default.

Consult your vendor's network card documentation to see if it can support unicast wake-up packets, and if it has to be specifically configured in the network adapter properties. Newer network cards are more likely to support this. This configuration might be referred to as Directed Packet, to differentiate it from traditional subnet-directed broadcast, which might be referred to as Magic Packet, although both methods of transmissions use the same Magic Packet format.

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For additional information, see Configuration Manager 2007 Information and Support.
To contact the documentation team, email SMSdocs@microsoft.com.

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