G+_Christopher Roman Posted July 29, 2014 Share Posted July 29, 2014 Hi KH, I've been having fun with this little breakout network tap I made. It's working fine so far but I'd love some more ideas of things I could do with it. My real question is: Why can't a gigabit Ethernet connection be passively tapped? I know it doesn't work from the experimenting I've been doing the last couple days but I'm too curious to leave it at that. Link to comment Share on other sites More sharing options...
G+_Fr. Robert Ballecer, SJ Posted July 29, 2014 Share Posted July 29, 2014 Put quite simply... the faster the connection, the harder it it to sniff. At the signaling rate of Gigabit Ethernet, a passive tap would unacceptably change the electrical characteristics of the wire while also introducing errors back into the line. Link to comment Share on other sites More sharing options...
G+_Christopher Roman Posted July 29, 2014 Author Share Posted July 29, 2014 Thanks Padre, I should have considered electrical interference. I actually had an instance where I connected a 30ft cord on the tap port with nothing on the other side and lost connection. I guess all that copper was leeching the signal off the tapped wires. I can imagine that at gigabit speed the cable would be too sensitive for a tap. Link to comment Share on other sites More sharing options...
G+_Akira Yamanita Posted July 30, 2014 Share Posted July 30, 2014 GigE signaling transmits 2 bits at a time instead of 1 using the same total voltage differential, making it more sensitive as Padre stated. However, the main reason is that each pair operates in full duplex. Link to comment Share on other sites More sharing options...
G+_Travis Hershberger Posted July 31, 2014 Share Posted July 31, 2014 GigE normally uses all 4 pairs of wire in the CATx cable as well, so most 100mbit network taps aren't even capable of passing the signal. Link to comment Share on other sites More sharing options...
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