Port Fa0/3 is configured to observe and allow only certain MAC addresses to associate
with the specific port, so in this example, Host A is denied access, but Host B is allowed to
associate with the port.
By using port security, you can limit the number of MAC addresses that can be assigned
dynamically to a port, set static MAC addresses, and—here’s my favorite part—set penalties
for users who abuse your policy! Personally, I like to have the port shut down when the security
policy is violated. Making abusers bring me a memo from their boss explaining why they
violated the security policy brings with it a certain poetic justice, which is nice. And I’ll also
require something like that before I’ll enable their port again. Things like this really seem to
help people remember to behave!
This is all good, but you still need to balance your particular security needs with the
time that implementing and managing them will realistically require. If you have tons of
time on your hands, then go ahead and seriously lock your network down vault-tight!
If you’re busy like the rest of us, I’m here to reassure you that there are ways to secure
things nicely without being totally overwhelmed with a massive amount of administrative