Understanding Wake On LAN

Version 6

    Verified Product Versions

    Endpoint Manager 9.5Endpoint Manager 9.6Endpoint Manager 2016.xEndpoint Manager 2017.xEndpoint Manager 2018.x

    What is Wake on LAN?

    Wake on LAN is a technology whereby a magic packet is sent to a client that is powered off.  If a network card detects a magic packet directed to its MAC address, the computer will power on.  Both the motherboard and network card must support Wake on LAN.  Wake on LAN must be enabled in the BIOS.

     

    How does LANDesk send a Wake on LAN magic packet?

    LANDesk can send a Wake on LAN magic packet in one of three ways:

     

    1. In the Delivery Method, configure the Multicast Domain Representative to send the Wake on LAN magic packet.

    2. When creating a Scheduled Task, check the Wake on LAN option. 
       
      Note:

      Checking this option when the Delivery Method has the MDR sending the magic packet can result in the WOL packet not being sent at all. 
    3. In the Console, right click on a device in the Network View and choose Wake on LAN.
       
      Note for options 2 and 3:

      This packet is sent from the computer running the Console.  If the console is open on the Core Server, the Core Server sends the packet.  If a Remote Console is open on a client machine, the magic packet is sent from that client machine running the Remote Console.  If these machines are on different subnets, different results may occur based on network settings.

     

    Is the Wake on LAN magic packet a TCP or UDP packet? Is it unicast or broadcast?

    The magic packet is a UDP broadcast packet.  Because the device is off, it does not have an IP Address therefore the magic packet must be broadcast packet.  Also, since the device is off, it cannot give a proper response to a TCP packet, therefore the magic packet must be UDP.  If the packet is crossing networks or subnets, it is a directed broadcast packet.  Note that routers are usually configured to drop directed broadcast packets.

     

    What port does LANDesk use to send the Wake on LAN magic Packet?*

    By default LANDesk uses UDP port 0.  This can be configured on the Core Server by going to Configure > Services > Scheduler.  The LANDesk Console must be restarted for this change to take affect.


     
    Note:

    The MDR always sends using port 0.  In previous version, this cannot be configured.  In 8.7 SP5 and 8.8 or later version, This can be configured by setting the following registry key and restarting the Targeted Multicast service on the MDR.

    HKEY_LOCAL_MACHINE\SOFTWARE\Intel\LANDesk\LDWM\Distribution\Multicast
    Type: DWORD
    Name: WOL Port


     
    Note:

    The web console will always send the magic packet from the core on port 0.

     

    What issues may prevent devices from receiving a Wake on LAN magic packet?

    1. If crossing subnets, routers are usually configured to drop directed broadcast packets. 

    2. LANDesk uses port 0 for the magic packet by default.  Many firewalls may block this port.  This port is configurable on the Core Server but not on the MDR. 

    3. The packet may be arriving but the network card or motherboard may not support Wake on LAN; or Wake on LAN is not enabled in the BIOS.

     

    Why does a device wake up from a Remote Console but not from the Console on the Core Server?

    This packet is sent from the computer running the Console.  If the console is open on the Core Server, the Core Server sends the packet.  If a Remote Console is open on a client machine, the magic packet is sent from that client machine running the Remote Console.  If these machines are on different subnets, different results may occur based on network settings.

     

    After changing the Wake on LAN port under Configure > Services > Scheduler, the change does not appear to have occurred.  What could be the problem?

     

    The problem could be two things:

     

    1. If sending the Wake on LAN packet from the console, the console must be restarted for this change to occur.

    2. This change does not modify the Wake on LAN port on the Multicast Domain Representative.  The Wake on LAN port on the MDR is not configurable and will always be set to 0.

     

    If network devices such as routers and switches are blocking directed broadcast and not a single machine on a particular subnet is powered on, will Wake on LAN work?

    If Wake on LAN magic packets cannot cross subnets, then at least one workstation must be available and running the LANDesk Agent with the Targeted Multicast feature.