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Posted by ScreamingMan on July 27, 2005, 8:47 am
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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
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Posted by on July 27, 2005, 10:41 am
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> 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.
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Posted by James Knott on July 27, 2005, 12:40 pm
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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.
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Posted by James Knott on July 27, 2005, 12:36 pm
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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.
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Posted by Patrick Schaaf on July 27, 2005, 1:57 pm
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> 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
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