Cisco switch port security

 Example:

int Fa0/1 

switchport mode access

!- maximum MAC address on port

 switchport port-security maximum 2

 switchport port-security

!- restrict MAC, logging  but don't shutdown port

 switchport port-security violation restrict

 switchport port-security mac-address sticky

 !- allowed MAC addresses

 switchport port-security mac-address sticky 702a.0371.96a6

 switchport port-security mac-address sticky 78d6.f355.eb4d

Show port security settings:

show port-security int Fa 0/1