In which mode does a network device increment the SecurityViolation counter when a violation occurs?

In the context of network security, particularly in regard to switch port configurations and violation handling, the SecurityViolation counter increments in restrict mode when a security violation occurs. This mode allows the network device to monitor traffic and enforce security policies without fully disabling the port, unlike shutdown mode, which completely disables the port.

In restrict mode, when a violation occurs — for instance, when an unauthorized device is detected — the device takes action to restrict the offending traffic while continuing to log the violations and increment the SecurityViolation counter. This logging is critical for network administrators to assess the frequency and nature of the violations for responsive measures, such as adjusting access controls or investigating potential security breaches.

Protect mode, while it also takes action on violations, does not increment the SecurityViolation counter, focusing instead on simply dropping packets from unauthorized sources without further logging. Secure mode is a more general term and does not specifically pertain to the handling of violation counters in the way restrict mode does. Thus, restricting unauthorized access while still monitoring and logging violations is a key function of restrict mode, making it the correct answer.