Refer to the exhibit.

According to theFortiSwitchOS 7.6 Administration Guideand theFortiLink 7.6 Study Guide, the Spanning Tree Protocol (STP) is automatically enabled on managed FortiSwitches to ensure a loop-free Layer 2 topology within the FortiLink fabric. When multiple physical paths exist between switches (as shown in the redundant connections between the Core and Access tiers), STP must block one of the paths to prevent a broadcast storm.

The behavior described in the exhibit—whereport3 on Access-1enters aDiscarding state—is a result of the STP election process. In a standard STP environment, switches elect aRoot Bridgebased on the lowestBridge Priority(or lowest MAC address as a tie-breaker). Once a root is established, other switches identify the " best " path to that root (the Root Port) and block all other redundant paths.

The provided exhibit shows that Access-1 has two paths to the core: one to Core-1 and one to Core-2. The fact that the path to Core-2 is discarded suggests that the STP topology was recalculated when Core-2 was enabled. In the context of Fortinet technical exams for this specific scenario,Option C (Core-2 has the lowest bridge priority)is the standard answer identifying that Core-2 ' s priority settings influenced the STP tree such that Access-1 ' s link to it was determined to be the redundant (alternate) path.

If the switches were configured withMCLAG (Multi-Chassis Link Aggregation), both physical links would be treated as a single logical trunk, and neither would be in a discarding state. However, without MCLAG, the system relies on bridge priorities to prune the loop.BPDU Guard (Option A)is incorrect because it would administratively shut down the port rather than placing it in an STP " Discarding " state.Option Bis incorrect as the switch would not appear in the managed topology if unauthorized.