trace laptop via hardware address

Archived from groups: comp.dcom.lans.ethernet (More info?)

Hello,

Might be the wrong group, but...

Is is possible, without having preinstalled tracing software, and
knowing the hardware address of the ethernet card, to trace a laptop? In
other words, can one find the IP address that the laptop is accessing the
web through?

Thanks

remove "spam" when replying
7 answers Last reply
More about trace laptop hardware address
  1. Archived from groups: comp.dcom.lans.ethernet (More info?)

    "ScreamingMan" <akiss@spam.life.uiuc.edu> wrote:
    > Is is possible, without having preinstalled tracing software, and
    >knowing the hardware address of the ethernet card, to trace a laptop? In
    >other words, can one find the IP address that the laptop is accessing the
    >web through?

    No, the MAC address disappears at the first {router,cable or DSL
    modem,switch,device} that the packets hit.
  2. Archived from groups: comp.dcom.lans.ethernet (More info?)

    ScreamingMan wrote:

    > Hello,
    >
    > Might be the wrong group, but...
    >
    > Is is possible, without having preinstalled tracing software, and
    > knowing the hardware address of the ethernet card, to trace a laptop? In
    > other words, can one find the IP address that the laptop is accessing the
    > web through?

    I'm not quite sure what you're asking for. If you have any communication
    with another computer, it's MAC address will be in your arp cache, for a
    period of time. You could run a script on your router, to scan the apr
    cache for the desired MAC address. Beyond that, you'll have to use some
    analyser app, such as ethereal at some point where the data passes. With
    the old non-switched ethernet, you could do that from anywhere on the
    network. Now, you'd likely have to do it at the router leading to the ISP
    or with a switch that provides port monitoring. Also, once a packet passes
    through a router, the original MAC is lost.
  3. Archived from groups: comp.dcom.lans.ethernet (More info?)

    William P. N. Smith wrote:

    > No, the MAC address disappears at the first {router,cable or DSL
    > modem,switch,device} that the packets hit.

    Not quite. Switches and other level two devices do not discard the MAC.
    Routers do. DSL is bit different, in that you usually have two different
    connections going over the line. One is the original ethernet connection
    to the modem, which will contain the MAC. The other is the PPPoE or PPPoA
    connection, which does not contain the MAC.
  4. Archived from groups: comp.dcom.lans.ethernet (More info?)

    "ScreamingMan" <akiss@spam.life.uiuc.edu> writes:

    > Is is possible, without having preinstalled tracing software, and
    >knowing the hardware address of the ethernet card, to trace a laptop? In
    >other words, can one find the IP address that the laptop is accessing the
    >web through?

    On the router which connects to the LAN that the laptop is plugged
    in, you can look at the ARP table to find this information (if the
    laptop has been active recently). If you don't have access to that
    router, you are pretty much out of luck, as the Ethernet "hardware address"
    has local network significance only, and is usually not transported on
    further hops.

    Also note that it is trivial to make any node use a different
    hardware address, by simple configuration.

    best regards
    Patrick
  5. Archived from groups: comp.dcom.lans.ethernet (More info?)

    ScreamingMan <akiss@spam.life.uiuc.edu> wrote:
    > Is is possible, without having preinstalled tracing software,
    > and knowing the hardware address of the ethernet card,
    > to trace a laptop? In other words, can one find the IP
    > address that the laptop is accessing the web through?

    If it's nearby (on the same ethernet), sure.
    You need to get access to ARP tables and caches.
    Ideally a RARP query.

    Once it has been routed (IPv4), the MAC is lost.
    Some implementations of IPv6 embed the MAC in the IP.
    So you cannot trace that laptop far.

    -- Robert
  6. Archived from groups: comp.dcom.lans.ethernet (More info?)

    ScreamingMan wrote:

    > Is is possible, without having preinstalled tracing software, and
    > knowing the hardware address of the ethernet card, to trace a laptop? In
    > other words, can one find the IP address that the laptop is accessing the
    > web through?

    If you mean a stolen machine, where you don't know which network it
    might be connected to, no. The MAC address does not pass through a router.

    Now, it might be that software that depends on a MAC key would have
    the MAC address sent through when it is registered, and you might find
    that it could be traced that way.

    -- glen
  7. Archived from groups: comp.dcom.lans.ethernet (More info?)

    Thanks, yes it was (is) a stolen machine. On the plus side, time for a new
    machine.

    Thanks


    "glen herrmannsfeldt" <gah@ugcs.caltech.edu> wrote in message
    news:wOadnR1hoa31G3XfRVn-sA@comcast.com...
    > ScreamingMan wrote:
    >
    >> Is is possible, without having preinstalled tracing software, and
    >> knowing the hardware address of the ethernet card, to trace a laptop? In
    >> other words, can one find the IP address that the laptop is accessing the
    >> web through?
    >
    > If you mean a stolen machine, where you don't know which network it
    > might be connected to, no. The MAC address does not pass through a
    > router.
    >
    > Now, it might be that software that depends on a MAC key would have
    > the MAC address sent through when it is registered, and you might find
    > that it could be traced that way.
    >
    > -- glen
    >
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