WOL over the internet - Networking

This is a discussion on WOL over the internet - Networking ; A computer A is connected to the internet by means of an ADSL modem/router, which is connected to A at A's Ethernet port. Assuming that we know the Ethernet address of this board, and that the hardware (motherboard, Ethernet board ...

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Thread: WOL over the internet

  1. WOL over the internet

    A computer A is connected to the internet by means of an ADSL
    modem/router, which is connected to A at A's Ethernet port.

    Assuming that we know the Ethernet address of this board, and
    that the hardware (motherboard, Ethernet board and BIOS configuration)
    does support WOL, would it be possible to wake up A from some other
    computer B in the internet? Would one have to open any specific ports in
    A's router/modem for the wake up packet to reach A, or would any port?




  2. Re: WOL over the internet

    Użytkownik H.K. Kingston-Smith napisał:
    > A computer A is connected to the internet by means of an ADSL
    > modem/router, which is connected to A at A's Ethernet port.
    >
    > Assuming that we know the Ethernet address of this board, and
    > that the hardware (motherboard, Ethernet board and BIOS configuration)
    > does support WOL, would it be possible to wake up A from some other
    > computer B in the internet? Would one have to open any specific ports in
    > A's router/modem for the wake up packet to reach A, or would any port?
    >
    >
    >

    AFAIK you need a router with WoL built-in. WoL works on layer-2 and your
    connection to router (from Internet) is in Layer-3. So with "normal"
    router there is no way to generate "magick" packet on LAN.

    W.P.

  3. Re: WOL over the internet

    On Thu, 28 Jun 2007 12:23:35 +0200, W.P. wrote:

    > Użytkownik H.K. Kingston-Smith napisał:
    >> A computer A is connected to the internet by means of an ADSL
    >> modem/router, which is connected to A at A's Ethernet port.
    >>
    >> Assuming that we know the Ethernet address of this board, and
    >> that the hardware (motherboard, Ethernet board and BIOS configuration)
    >> does support WOL, would it be possible to wake up A from some other
    >> computer B in the internet? Would one have to open any specific ports
    >> in A's router/modem for the wake up packet to reach A, or would any
    >> port?
    >>
    >>
    >>

    > AFAIK you need a router with WoL built-in. WoL works on layer-2 and your
    > connection to router (from Internet) is in Layer-3. So with "normal"
    > router there is no way to generate "magick" packet on LAN.


    It can work, at least with some implementations:
    http://forums.speedguide.net/showthread.php?t=141643

    OP will need to set up a port forward on the router to 0, 7 or 9 UDP,
    depending on the WOL implementation of the target machine.
    http://en.wikipedia.org/wiki/Wake-on-LAN


    Alternatively, with a Linksys WRT54G running third-party firmware (I use
    Sveasoft Alchemy), it is possible to ssh into the router from the internet
    and use the WOL utility on the router to send the magic packet to the LAN.



    --


    --
    Posted via a free Usenet account from http://www.teranews.com


  4. Re: WOL over the internet

    On Thu, 28 Jun 2007, in the Usenet newsgroup comp.os.linux.networking, in
    article , H.K. Kingston-Smith wrote:

    >A computer A is connected to the internet by means of an ADSL
    >modem/router, which is connected to A at A's Ethernet port.


    You will have to look at that "modem/router" as that's where the
    difficulty will lie.

    > Assuming that we know the Ethernet address of this board, and
    >that the hardware (motherboard, Ethernet board and BIOS configuration)
    >does support WOL, would it be possible to wake up A from some other
    >computer B in the internet?


    Yes

    >Would one have to open any specific ports in A's router/modem for the
    >wake up packet to reach A, or would any port?


    The "Wake-On-LAN" "magic packet" is merely specified as having the
    target NIC adapters MAC address repeated 16 times in the data field.
    Thus, the packet can be anything you can send - a ping is often
    easiest to create, but any protocol that your network allows is
    equally acceptable, such as TCP, UDP, IPX, Appletalk, what-ever.
    Donald Becker used to have a program called "ether-wake" as part of
    the "diag-ether" tarball.

    THE PROBLEM is getting the router to deliver the packet. For _any_
    data transmission on an Ethernet type of network, the local _sending_
    station (in this case, the "modem/router") has to know the MAC address
    to send it to. The packet must either be a broadcast (and the sending
    station accepting/allowing this concept), OR the packet must be a normal
    "unicast" directed at the MAC address of the destination host.[1] The
    operating system remembers this data in an ARP cache (try "/sbin/arp -a"
    to see the current MAC/IP relationships your system knows about). The
    normal problem about the ARP cache is that Internet standards
    (specifically RFC1122 Section 2.3.2.1) requires this data to expire in
    a timely manner - the recommended value is "on the order of a minute".
    So, a minute after the router stops talking to host $FOO, the ARP cache
    entry should disappear. Thus, if some _local_ host wants to "talk" to
    host $FOO, it either must have the MAC/IP entry in it's arp cache, OR it
    sends an ARP request (a simple Ethernet broadcast) to try to get this
    information.

    12:38:06.114000 arp who-has 192.0.2.21 tell 192.0.2.133

    The rub come from the fact that "192.0.2.21" is powered down, and won't
    answer this ARP request. The result is that "192.0.2.133" can't talk to
    "192.0.2.21" because it can't determine the MAC address to send packets
    to.

    WHAT TO DO? There are two ways around this problem. The first is to
    send the WOL packet to the network broadcast address. This is a less
    than optimal solution, as a LOT of routers are configured to not send
    such packets (abuse prevention). The other solution is to use a
    static arp entry on the local "sending" station. For a common Linux box,
    see the arp(8) man page, and look at the "-s" option. Most routers have
    a similar command/capability. NOTE: On a switched network (as opposed
    to coax or using a hub), the network switch _may_ also require a static
    entry - see the manual/documentation for your network switch.

    Old guy

    [1] On a non-switched network (coax or hub), the packet _can_ be sent
    to any MAC address on the local wire. A switch would not forward this
    packet to all hosts, thus the actual destination MAC address is needed.

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