Topic last updated—November 2007
This topic provides troubleshooting information to help you resolve issues when Wake On LAN in Configuration Manager does not successfully wake up computers.
Computers Do Not Wake Up Because the Computer Does Not Support Wake On LAN Transmissions
A successful deployment of Wake On LAN depends on many factors external to Configuration Manager. On the computer itself, these include the following:
- The network adapter (and driver) supports the
Magic Packet format that is used for Wake On LAN technology.
- If you are using unicast as your transmission
method rather than subnet-directed broadcast, whether the network
adapter (and driver) supports this.
- The appropriate configuration has been
performed to support wake-up packets. The configuration will be
vendor-dependent and is likely to include configuring the BIOS and
the driver or adapter properties in Windows. However, for older
network adapters, it could include connecting wires or moving
jumpers on the adapter.
Note If you want to wake up computers using Wake On LAN in Configuration Manager, ensure that the BIOS is not configured with a password. If a BIOS password is set, the computer cannot complete startup until the password is supplied manually.
Refer to your vendor's documentation for information about support for wake-up packets and required configuration.
Computers Do Not Wake Up Because the Network Infrastructure Does Not Support Wake On LAN Transmissions
A successful deployment of Wake On LAN depends on many factors external to Configuration Manager. On the network, these might include (but are not limited to) the configuration of firewalls, routers, and switches to allow the wake-up transmission packets using the port number specified in Configuration Manager.
|Application-level firewalls such as ISA Server cannot detect wake-up transmissions as a protocol, so a protocol rule of "Allow all IP traffic" will not be sufficient to forward wake-up packets. Instead, configure an IP filter rule to forward UDP packets on the port number specified in Configuration Manager, with the source address of the site server configured for Wake On LAN.|
Consult your networking team and vendor documentation for information about allowing the wake-up packets to traverse the network. Wake-up transmissions use UDP rather than TCP, which means that the sending site server has no knowledge of whether the packets reach the intended computers. You can use a network monitor to confirm whether the wake-up packets traverse the network successfully. For more information, see Determine Whether Wake-Up Packets Traverse the Network for Wake On LAN.
The default port number used for Wake On LAN in Configuration Manager 2007 is 9, but this can be changed to a custom port number. For procedural information about verifying or changing the port number, see How to Configure the Ports Used for Wake On LAN.
Computers Do Not Wake Up Because the Client Has Not Completed a Hardware Inventory Cycle
The wake-up packets sent by the site server are constructed using the MAC address of the target computer, using hardware inventory information previously collected. If hardware inventory is not enabled for the site or if the target computer is a new Configuration Manager client that has not yet sent its inventory information back to the site, the site server cannot construct the wake-up packets.
Ensure that hardware inventory is configured and that clients that need to be woken up have completed at least one hardware inventory cycle.
For more information, see How to Configure Hardware Inventory for a Site.
Computers Do Not Wake Up Because They Have Changed Their IP Address Since the Last Hardware Inventory Cycle
When the site server uses unicast as the wake-up transmission method, it sends the wake-up packet to the target computer's last known IP address (from hardware inventory). If the target computer no longer has the same IP address, it will not receive the wake-up packets.
When the site server uses subnet-directed broadcast as the wake-up transmission method, it sends the wake-up packet to the target computer's last known IP subnet address (from hardware inventory). If the target computer no longer has the same subnet address (for example, it is a client that frequently roams in the Configuration Manager hierarchy), it will not receive the wake-up packets.
Increasing the DHCP lease time and configuring the hardware inventory schedule to run more frequently can help to reduce the likelihood of sending wake-up packets to out-of-date addresses.
Additionally, if computers frequently change IP addresses but keep the same subnet address, selecting subnet-directed broadcast rather than unicast as the transmission method will prove more effective in waking up computers.
For more information, see the following topics: