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I am
trying to passively sniff a 100Mb full duplex ethernet (without disturbing the
signal in any way, setting up as a bridge is not acceptable as it dramatically
alters the problem I am trying to solve (I have already tried it)), I had a look
through the archives and there are some posts about this, basically using two
ethernet cards and connecting one to sniff traffic going one way and the
other for the other way.
I did
not see any explanation on how to do this, I am guessing that if I wire the TX
pair from device A into the RX pair of device B and also into the RX on the
first sniffer card, and then wire the TX from B into RX of A and RX on the
second sniffer card, then I will probably get errors due to signal reflections
and interference where the signal is split.
I have
thought of using two hubs to split the two signals, but I am not sure how that
will work with things like the link pulses, and the Speed / Duplex
autonegotiation information as to do this the hub would be receiving data from a
port where there is no TX pair connected, and transmitting where there is no RX
pair connected.
Has
anyone actually done this? If so, how?
Also,
I would like to monitor the link pulses, the Speed / Duplex autonegotiation, and
the packets that were discarded by the NIC at hardware level due to various
errors (runt, jabber, alignment, CRC, etc... Even when there is no "start frame
delimiter" after the preamble). Basically any time any sort of carrier is
detected on the wire I would like it logged with a time that I can match up with
other packets in the ethereal capture. I am having difficulty locating equipment
to do this, and if there is a relatively cheap way of doing this with linux then
I would like to try it. Also, if there is a relatively expensive way of doing it
then I would like to know about that too.
Thank
you
Graham
Crowe
Electrical Engineer
BHP
Steel
EOM
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