In FortiSwitchOS 7.6,Loop Guardis a Layer 2 loop detection mechanism primarily designed to protect access ports from unintended network loops. In itsoriginal implementation, Loop Guard only detected loops on thenative VLAN, which limited its effectiveness in environments using multiple tagged VLANs. To address this limitation, Fortinet enhanced Loop Guard by introducing theMAC move detection feature, as documented in the FortiSwitchOS 7.6 Administrator Guide.

TheMAC move optioninstructs the FortiSwitch to monitor for repeated MAC address flapping events across ports or VLANs. Such MAC movement is a strong indicator of a Layer 2 loop. However, this enhanced detection mechanism isdisabled by defaultand must be explicitly enabled by configuring aMAC move threshold greater than zero.

According to the FortiSwitchOS 7.6 Administrator Guide (page 164), enabling MAC move allows Loop Guard to detect loops beyond the native VLAN. Furthermore, the guide explicitly states (page 166) thata MAC-Move value of 0 indicates that the MAC move feature is not enabled. This means the switch is not monitoring MAC address movement as part of its loop detection logic, even though Loop Guard itself may still be enabled on the port.

Therefore, a MAC-Move value of 0 does not indicate that Loop Guard is disabled or inactive, nor does it imply VLAN-wide port shutdown behavior. It strictly confirms thatMAC move detection has not been enabled, makingOption Cthe correct and fully verified answer based on FortiSwitchOS 7.6 documentation.