Wake-on-Lan across router boundaries | Feb/18/2022
Mac addresses in other IP subnets cannot be
reached directly. For this reason, the broadcast address of the
remote network must be included when calling the wake-up command. If
a computer with the Mac address 0A-00-27-A0-0E-14
is to be woken up from the network 10.4.0.0 with
the subnet mask 255.255.0.0 (Class B), the wake-up
command is as follows
wol.exe 0A-00-27-A0-0E-14 10.4.255.255
Execute this command with the command line tool wol.exe, which is included with the WakeOnLanTool and the PingTool.
However, this alone is not enough. The network must be configured for this, since the router does not forward the Magic Packet by default.
Example configuration Cisco router
To transport the Magic Packet across router boundaries, the routers must be configured for this. For Cisco routers, for example, this can be achieved with the ip-directed broadcast command on the LAN interface in the target LAN, i.e. the subnet in which computers are to be woken up. In order not to let all broadcasts pass through for security reasons, an access list should be configured in which the machines authorized to send are limited. If, for example, only a specific server - in this case the Wake-On-Lan server with the IP address 10.2.1.1 - is to be authorized for network-wide broadcasts, the following configuration is used:
Router(config-if)#ip directed-broadcast 101
Router(config)#access-list 101 permit udp host 10.2.1.1 any
Check the functionality
To see if a Wake-On-Lan packet has crossed the router boundary, you can look at the "matches" within the access-list using show access-lists:
Extended IP access list 101
10 permit udp host 10.2.1.1 any (12 matches)
If the number of matches increases when the wake-up command is sent, it is certain that the Magic Packet has overcome the router. Alternatively, a Wireshark measurement on the PC helps. If the packet can be recorded here, but the PC shows no movement, this is a sure indication that the problem is not caused by the network. Read also the article Wake-On-Lan Windows 10, which describes the configuration of Wake-On-Lan in 8 steps.
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Kategorie: Wake On Lan other subnet, Wake On Lan other network, WOL other subnet
Problem: Wake On Lan not working other subnet