WOL over Internet - without Router customization

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I know that there are already plenty of issues regarding WOL over the Internet but I thinkt that mine is still a little bit different. Because I am using an internet provider which doesn't allow me to change anything on my router (this is really annoying - my dad bought it... times ago) I called my provider and they told me that it's not possible to open ports (for WOL) with the packet we're using. So either we'll have to switch to another packet or I find another solution about how to use WOL without customizing the router.

Are there any solutions/hints out there? ;)

Ripei

Posted 2011-07-06T10:24:51.660

Reputation: 133

Answers

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Wake On LAN packets are designed to be routed at what's known as the link layer, where network devices local to each other communicate.

It is simply not possible to perform a Wake On LAN request over the internet unless you have a device on the recipient network that can route the magic Wake On LAN packet to the requisite device, or the system itself is connected directly to the internet without the use of a cable modem or router.

Typically this will be another system behind a routed network or a router configured to let this packet through to your internal network on your behalf.

As internet routing is only concerned with TCP/IP and UDP/IP (the two ways of transferring data online, TCP having validation and UDP not), lower level data that isn't relevant to the recipient network isn't typically routed, so as such magic packets for computer awakening aren't received.

If you are curious, there is more information on the OSI model which defines the seven layers involved with networking: http://en.wikipedia.org/wiki/OSI_model

Ruairi Fullam

Posted 2011-07-06T10:24:51.660

Reputation: 2 284

You actually can send a WoL magic packet over the Internet, if you already know the MAC address of the sleeping machine. WoL-capable NICs just look for six bytes of 0xFF followed by their own MAC address sixteen times. You can put that in the payload of a UDP datagram to the IP address of the sleeping machine. It helps to have the router for that subnet have a static ARP mapping for that host, so it always knows which MAC address to send it to without having to do an ARP lookup first. This doesn't solve @Ripei's "without customizing the router" condition though. – Spiff – 2011-07-06T20:08:16.183

With no disrespect, this isn't contrary to what I've posted. I think your downvote was unfair. – Ruairi Fullam – 2011-07-06T20:12:31.330

Your post really makes it sound like you think WoL magic packets can't be routed from off-subnet, but that's absolutely not true, which is what I tried to explain. Needing a static ARP mapping on the router so your UDP or ICMP magic packet gets through is a far cry from needing a magic-packet originator on the same subnet as the sleeping machine. – Spiff – 2011-07-07T02:15:30.677

OK, I will clear up my post to further clarify that, but in this case the question asker does not have the ability to configure his router. – Ruairi Fullam – 2011-07-07T13:22:25.063

Spiff: I've updated the answer. Please let me know if this is clear enough now. – Ruairi Fullam – 2011-07-07T13:27:55.743

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The first four layers of the OSI model are:

  1. Physical (the wire or other physical medium to transmit across)
  2. The Data Link layer (this is where a typical switch works, and the WOL works).
  3. The Network Layer (routing)
  4. The Transport Layer (TCP/UDP the protocols the connection will use to communicate).

As you can see, what you want to happen, happens at Layer 2, before it could ever route at Layer 3, and communicate at Layer 4.

http://en.wikipedia.org/wiki/OSI_model

KCotreau

Posted 2011-07-06T10:24:51.660

Reputation: 24 985

WoL is a layer-2 concept, but WoL NICs look at all packet data, including application layer data for the magic pattern. So you can wake a machine from off-subnet if you already know its MAC address, and if you can keep the router from forgetting the ARP mapping for the machine. – Spiff – 2011-07-06T20:11:12.593

@Spiff Read the first line of his question: "regarding WOL over the Internet". Are you telling me he will be able to do that, if so, please post an answer, and I will upvote it. His question included the need to route it. – KCotreau – 2011-07-06T20:14:00.813

Yes, you can put the WoL magic pattern inside a UDP/IP datagram or even an ICMP Echo (ping) datagram and it routes just fine, just like any other UDP/IP datagram or ping request, and it will wake the machine. The only tricky part is making sure the layer-2 delivery happens, which means you can't let the router forget the ARP mapping for the sleeping host. I don't have a solution to that part given his "can't customize the router" limitation, so I'm not posting an Answer. I'm just trying to bust the myth of "WoL magic packets can't be routed". – Spiff – 2011-07-07T02:08:41.727

Asked: 2011-07-06T10:24:51.660

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Active: 2011-07-07T13:27:38.270