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I'm currently working away from home and I want to power on my home PC (running Windows 11). The PC is currently off, but it has Wake-on-LAN (WOL) enabled so if I send it a WOL packet it will turn on.

I can VPN into my home network and send the packet, but the problem is I have not written down the MAC address, so I don't know where to send the packet. Is there a way I can find the MAC address, e.g., some form of layer 2 broadcast that a NIC listening for WOL packets will reply to? Or alternatively, can a WOL packet be sent to the MAC equivalent of a broadcast address?

I have checked the obvious things, e.g., looking at the DHCP logs and NAT sessions logs to see if I can find the MAC address in those, but with no luck. The only way I will be able to find the MAC address is if there is some way to probe for it on the network.

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  • Have you run this command before in the past? Is it in a CLI history anywhere that would have the MAC ?
    – Criggie
    Commented Nov 9, 2022 at 18:28
  • ARP caches on other devices may contain the info, but I doubt any will keep it for 2 weeks. DHCP leases should also have the info, and are more likely to still be around. What DHCP server is it?
    – jcaron
    Commented Nov 10, 2022 at 0:34
  • This doesn't help you now, but this is one reason I set DHCP Reservations for many of my computers - if I need the MAC Address, I can look in the DHCP Server configuration.
    – Moshe Katz
    Commented Nov 14, 2022 at 19:24

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The MAC address really should be in your DHCP server's logs. (If not as the MAC itself, then as the Client-ID.) Otherwise they're rather useless as DHCP logs.

It takes around 1 minute to spam the network with WOL packets for all possible XX:XX:XX:_:_:_ addresses (i.e. for a single OUI). If you roughly know the manufacturer of your Ethernet NIC, you can probably find the right MAC address via brute-force in… probably 10 hours if it's Intel (who has ~575 OUIs).

Is there any way I can find the MAC address e.g. some form of layer 2 broadcast that a NIC listening for WOL packets will reply to?

No, sleeping NICs almost never send anything at all. (Though I've seen old Dell laptops in 2008 that would periodically broadcast ECTP frames while asleep...)

Or alternatively can a WOL packet be sent to the MAC equivalent of a broadcast address?

WOL packets can be broadcast (and usually are) but they must include the NIC's MAC address as part of the packet payload – otherwise it's not a valid WOL packet.

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  • Sadly I've been away for two weeks and I don't keep the DHCP logs for that long. I will look at a brute force approach. Thanks :-)
    – John Rennie
    Commented Nov 9, 2022 at 9:18

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