It’s usually not a good thing to have your switches available for anyone to just plug into and
play around with. I mean, we worry about wireless security, so why wouldn’t we demand
switch security just as much, if not more?
But just how do we actually prevent someone from simply plugging a host into one of
our switch ports—or worse, adding a hub, switch, or access point into the Ethernet jack
in their office? By default, MAC addresses will just dynamically appear in your MAC
forward/filter database and you can stop them in their tracks by using port security!
Figure 10.5 shows two hosts connected to the single switch port Fa0/3 via either a hub
or access point (AP).