About Software Distribution Wake On LAN

Artigo
05/03/2011

Applies To: 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

Wake On LAN in Microsoft System Center Configuration Manager 2007 supports the following scenarios:

Sending a wake-up transmission prior to the configured deadline for a software update deployment.
Sending a wake-up transmission prior to the configured schedule of a mandatory advertisement, which can be for software distribution or a task sequence.

When software update deployments are configured for Wake On LAN, wake-up packets will be sent only to computers that require the software updates.

Each site must be independently configured for Wake On LAN, by using either unicast or subnet-directed broadcast as the transmission method. Wake-up packets are sent from the primary site server to computers that are assigned to its site.

Note

Wake-up packet transmissions are sent only from primary site servers. You cannot configure secondary site servers or other computers that are acting as proxies to send wake-up packets.

Wake On LAN is not supported with Internet-based client management, and it does not support maintenance windows.

Prerequisites for Wake On LAN

Wake On LAN in Configuration Manager 2007 has both external dependencies and dependencies within the product.

Dependencies External to Configuration Manager 2007

Dependency	More Information
Network cards must support the standard magic packet format.	All network cards that have the Windows Logo certificate support this magic packet format.
Computers must be configured for wake-up packets on the network card and in the computer BIOS.	Refer to your hardware vendor's documentation for information about how to configure this.
If you are using Wake On LAN with subnet-directed broadcast, all routers between the site server and target computers must allow IP directed broadcasts, and support IPv4.	Typically, routers are configured to not allow subnet-directed broadcast. Subnet-directed broadcasts are not supported with IPv6.

Network cards must support the standard magic packet format.

All network cards that have the Windows Logo certificate support this magic packet format.

Computers must be configured for wake-up packets on the network card and in the computer BIOS.

Refer to your hardware vendor's documentation for information about how to configure this.

If you are using Wake On LAN with subnet-directed broadcast, all routers between the site server and target computers must allow IP directed broadcasts, and support IPv4.

Typically, routers are configured to not allow subnet-directed broadcast.

Subnet-directed broadcasts are not supported with IPv6.

Configuration Manager 2007 Dependencies

Dependency	More Information
Hardware inventory must be enabled, and must have completed an inventory schedule.	Collecting Hardware Inventory Configure the Hardware Inventory Client Agent
Clients must be Configuration Manager 2007 clients.	Clients running Systems Management Server (SMS) 2003 do not support Wake On LAN

Hardware inventory must be enabled, and must have completed an inventory schedule.

Collecting Hardware Inventory

Configure the Hardware Inventory Client Agent

Clients must be Configuration Manager 2007 clients.

Clients running Systems Management Server (SMS) 2003 do not support Wake On LAN

Sleep States

Sleep states describe the possible power states for a computer, as described in the following table:

Sleep State	Description
S0	The computer is on and fully functional.
S1	The computer appears to be off with the CPU stopped. RAM is refreshed, and the computer is running in a low power mode.
S2	The computer appears to be off with the CPU stopped. RAM is refreshed, and the computer is running in a lower power mode than S1.
S3 - Standby	The computer appears to be off with no power to the CPU. RAM is in slow refresh.
S4 - Hibernate	The computer appears to be off with no power to the hardware. System memory has been saved as a temporary file on the hard disk.
S5 - Off	The computer is off with no power to the hardware, and the operating system has been shut down without saving system memory to disk.

Wake On LAN in Configuration Manager supports waking up computers in sleep states S1 through S5.

Wake On LAN in Configuration Manager does not return computers to a sleep state. On wake-up, the Configuration Manager client registers the system as busy for the specific wake-up task it received, until the task is completed. This prevents the computer from going back into a sleep state based on its power management settings before the task can be completed.

You can use power management schemes to configure computers to shut down or hibernate after a period of activity. Windows Vista supports power management schemes through Group Policy.

Unicast Wake-Up Packets

Unicast, as the transmission method for sending wake-up packets to a computer in a Configuration Manager 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.

Note

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.

Subnet-Directed Broadcast Wake-Up Packets

Subnet-directed broadcasts, as the transmission method for sending wake-up packets to a computer in a Configuration Manager site, use the MAC address and IP subnet address of the target computer from hardware inventory. The wake-up transmission is sent to the computer's last known subnet, and it is then broadcast to all computers on that subnet. For this method to be successful, all intervening routers must be configured to forward subnet-directed broadcasts. During this broadcast, the computer that has the MAC address specified in the wake-up transmission will respond.

Because this transmission method uses the subnet address rather than the IP address, it will succeed if the target computer has changed IP addresses but remained in the same subnet. The use of subnet-directed broadcasts is the more traditional method of sending wake-up packets, so this transmission method might be more compatible with a wider range of computer network adapters than transmitting wake-up packets by using unicast. However, subnet-direct broadcasts are not supported with IPv6, and are often disabled on routers.

Important

If you are using subnet-directed broadcasts as the Wake On LAN transmission method, it is highly recommended you include the additional security measure of allowing only the Configuration Manager site server to send subnet-directed broadcast traffic by using a non-default port number for the wake-up packets.

Wake On LAN in Configuration Manager Hierarchies

Each site in the Configuration Manager hierarchy can be independently enabled or disabled for Wake On LAN. When a Wake On LAN activity is targeted at client computers, the wake-up transmission is sent only to client computers that are assigned to that site. Because advertisements and software update deployments are inherited by child sites, the site server in the child site is responsible for sending the wake-up transmissions to its assigned clients if the site is enabled for Wake On LAN.

If the child site is not enabled for Wake On LAN, client computers in that site will not be sent wake-up packets.

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