MIB: IF-MIB.
The current operational state of the interface:
-  The testing (3) state indicates that no operational packet scan be passed.
-  If ifAdminStatus is down (2), then ifOperStatus should be down (2).
-  If ifAdminStatus is changed to up (1), then ifOperStatus should change to up (1), provided the interface is ready to transmit and receive network traffic.
-  It should change to dormant (5) if the interface is waiting for external actions, such as a serial line waiting for an incoming connection.
-  It should remain in the down (2) state if and only when there is a fault that prevents it from going to the up (1) state.
-  It should remain in the notPresent (6) state if the interface has missing components (typically, hardware).