What is Wake-on-LAN ?
CA Client Automation - All Versions
Wake-on-LAN provides the capability to remotely power on systems in soft off state supporting Wake-on-LAN by simply sending a wake-up frame.
- Wake-on-LAN-enabled Ethernet LAN adapter card
- Wake-on-LAN-enabled Motherboard
- Wake-on-LAN option must be enabled in the BIOS Power Management
Boot the PC and view the BIOS. Change the BIOS parameters to enable power management to support Wake-on-LAN. You will have to read the documentation that came with your PC for more information about accessing and editing the BIOS. Usually it is labeled "WOL" and is found under the "power management" section. But it may also be labeled "PME" or "Wake (up) on LAN/Ethernet/PME#", or found under a different BIOS section
- System must be in a Soft-Off state.
Caf sendwol can be used to test if the target machine can received wake on LAN datagrams. This sends a Wake-on-LAN packet to the specified machine. If the machine is configured for Wake-on-LAN and is presently turned off, it will turn on and boot
caf sendwol <mac address> <subnet/IP address > <subnetmask>
The Mac address is in the format 0A:7B:22:3D:4E:5F.
The subnet and mask are in dotted quad format, for example, 18.104.22.168.
For example to send a wake on LAN datagram, to a machine whose IP is 192.168.1.1 and subnet mask 255.255.255.0 and Mac address 0A:7B:22:3D:4E:5F, the command would be as
Caf sendwol 0A:7B:22:3D:4E:5F 192.168.1.1 255.255.255.0
When you create a new policy, the policies for wake on LAN are present at: DSM->Common Components-> CAF->Wake-on-LAN.
The Wake-on-LAN policy group lets you set policies for remotely and automatically powering up computers in your enterprise. You can modify the policy values by double-clicking a policy to display the Setting Properties dialog.
Indicates whether broadcasts are used to wake computers.
If this is true then broadcasts are used to wake up computers else Targeted Method is used.
Specifies the UDP port to which Wake-on-LAN (WOL) datagrams are to be sent.
This can be changed to any other value.
Modify these setting and send this policy to the target machines.
When we send a package, it would send the wake on LAN frame along with the package.
There is no way wake on LAN can be disabled.
- Initially to test we can use caf sendwol command to see if the machine wakes up.
- Once the machine wakes up using this command, we send the wake on policy to the target computers and then send the package. If no policy is sent, then the default policy would be used.
- If the machine does not wake up then check if motherboard, NIC, Bios are enabled for WOL and that the system is in soft off state.
- Otherwise if there are no routers, then check the Arp cache on the Manager machine by using the command arp -a . This would contain the IP address to Mac address mapping. If the entry for that machine is not present, try adding the entry manually by using arp -s command. Then try sending the package and see if it works.
- This arp cache would be cleared at regular intervals.
- If there is a router involved , then we may have check the router settings
On the router that is connected to the server that sends the WOL broadcast, apply these global commands to control what broadcasts are forwarded. The port 137 and 138 are Windows ports that can cause browse problems if forwarded. The port 68 is used for DHCP.
ip forward-protocol udp XXX (port used by WOL)
no ip forward-protocol udp 137 (disable default)
no ip forward-protocol udp 138 (disable default)
no ip forward-protocol udp 68 (disable default)
On the interface connected to the WOL server apply the helpers. You can use many. The example would forward broadcasts to the 10.10.0.0/16 subnet.
ip helper-address 10.10.255.255
On the interface connected to the PCs that need to receive the broadcast add the ip directed broadcast command.
ip adress 10.10.0.1 255.255.0.0
If the server has successfully sent the wake on LAN datagrams, then TRC_USD_SDSERVER log would contain the below information:
110406-11:48:10.6655851L|005404|00001160|SDServer |cfCafApi | |000000|INFO | CCFCafApi::Trigg - Sending Wake-On-Lan Packet
110406-11:48:10.7458852L|005404|00001160|SDServer |CcnfAgentApi |CCcnfAgentApi.cpp |001347|DETAIL | GetParameterValueInt(itrm/common/caf/wol, broadcast, ..., NULL) successfully completed. Parameter value: 1
Which method to use :
Enabling broadcasts may cause lot of traffic in the network as WOL packets will be sent to all the machines in the subnet specified. This may clog the network if there are too many machines in the specified subnet.
A WOL packet is broadcast to all the machines in the subnet and only the intended machine receives the packet.
The main disadvantage to using targeted method occurs in a networked environment involving Routers. Routers rely upon PC's periodically transmitting an ARP protocol packet containing their network card's MAC address (which is unique to each network card). Routers use this information when "routing" messages from outside of a network segment to machines within the segment. In order for Routers to work efficiently they operate a system of routing tables and internal caches that expire and remove entries not heard from or contacted within a specified timeframe. If a PC has remained in a powered off state beyond this time you will be unable to wake it up if the originating request is outside of the network segment because the Router cannot determine where to send it. However, the Router can be configured to increase the inactivity time, which will reduce the likelihood that the switched off machine is removed from the routing table.
If you wish to disable WAKE on LAN this is controlled in the DSM Policy
- Domain/Control Panel/Configuration/Configuration Policy/Default Computer Policy/DSM/Software Delivery/Scalability Server
set the Job Check: Disable-Wake-On-LAN to true
reseal the policy