I have a hub here that I use all the time with Wire Shark. Sometimes I
need to help someone debug something in the field, and they don't have a
hub, and they are getting hard to come by.

Since 10/100 Ethernet uses two pair, one for transmit, and one for
receive, it SEEMS like it should be possible to make a resistive hub where
each transmit pair drives the receive pairs of the other two ports (total
of 3 ports). I've done similar resistive networks for audio splitting
while maintaining impedances. But, I haven't figured out whether this
would work or what the resistor values would be. I did find a passive hub
using a bunch of diodes, but it seems like resistors should work. I also
see Ethernet taps where there are four ports. Data going one way between
the other two ports shows up on one of the monitor ports while data going
the other way shows up on the other monitor port. This requires two
Ethernet ports on the computer running WireShark, which is a pain.

So, any ideas on this? Is it possible to use resistive splitters to make a
passive hub?

Thanks!

Harold


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