Re: WakeOnLAN across WAN

In article <6ep8fgF835n8U1@xxxxxxxxxxxxxxxxxx>,
Adrian C <email@xxxxxxxxxxxx> wrote:

David Sankey wrote:

If your router remembers where the relevant machine is (which is what
you circumvent by going to a broadcast packet).


Nope and yeah :-)

The magic packet by definition has a broadcast frame* and is carried
over the internet as such to the external IP of the router. The router
can direct "port forward" this broadcast packet to the specific
interface. Hence "Subnet Directed Broadcast".

It does not mean the need to broadcast it to every machine on the subnet
- it's just a packet which looks like a broadcast!

* - http://en.wikipedia.org/wiki/Wake_on_lan

Well, as that wikipedia page says: "The Magic Packet is a broadcast
frame containing anywhere within its payload 6 bytes of ones FF FF FF FF
FF FF followed by sixteen repetitions of the target computer's MAC
address."

The important thing is this payload. What you need is that a packet is
visible on the network interface of the machine which you wish to wake
which contains (somewhere) this specific data.

You achieve this either by having the switch in your router remember
which LAN port this machine had been on, or by broadcasting it to all
ports.

That at the time it is woken the machine has no IP address is not
important, what is important is the network activity on its network port.

If you have port forwarding already defined, I would certainly try a WOL
packet sent to this port on the router's WAN interface. Given the lack
of activity on the LAN there is a chance that the switch remembers which
port previously corresponded to the machine in question (or it might be
possible to disable the flushing of this information).

Or you can see if you can trick your router into broadcasting, by
forwarding any port you like on your external interface to any port you
like on the broadcast address for your LAN (i.e. something like
192.168.0.255).

A final way to frig this with a directed packet is if you have a machine
that is always on on your LAN (in my case, a networked all-in-one). If
you put this machine on a hub (NOT switch) and have the machine to be
woken connected to this hub, it will see the magic packet sent to the
known machine.

Good luck,

Dave
.

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