want to detect the new hooked-in device in LAN

[saya]

Hello all!
I'm now using mactrack plugins and now have it working...
but I am not quite sure about some data
like in the attached pic, what do the "total IPs" and "last duration" mean?
and I want to monitor the ports of a switch... can I be notified once there is a new device hooked to any port? How can I atrieve that?

Thanks a lot!!!