There is a limit of 500 MAC Lockdowns that you can safely code per switch. To truly lock down a MAC address it would be necessary to use the MAC Lockdown command for every MAC Address and VLAN ID on every switch. In reality few network administrators will go to this length, but it is important to note that just because you have locked down the MAC address and VID for a single switch, the device (or a hacker “spoofing” the MAC address for the device) may still be able to use another switch which hasn’t been locked down.