Exam NSE5_FSW_AD-7.6 Topic 1 Question 3 Discussion

According to theFortiSwitchOS 7.6 Administration Guideand theFortiSwitch 7.6 Study Guide, Multichassis Link Aggregation (MCLAG) provides node-level redundancy by grouping two physical switches together so that theyappear as a single logical switchto the rest of the network. This logical representation is critical for preventing Spanning Tree Protocol (STP) from blocking redundant uplinks from downstream client switches.
To achieve this " single switch " appearance, the MCLAG peer switches synchronize their STP state andshare the same Bridge ID, which consists of a synchronized bridge MAC address and the same bridge priority. As shown in the exhibits for Core-1 and Core-2, both switches are configured with aBridge MAC of
02090f000701and aPriority of 20480. Because they possess identical identification parameters, each physical switch in the peer group locally recognizes itself as part of the root bridge entity for the MSTP region.
This behavior is intentional and is a fundamental characteristic of MCLAG design in FortiSwitchOS. It ensures that any downstream device, such as Access-1, receives BPDUs with the same bridge ID from both Core-1 and Core-2, thereby treating them as a single high-availability neighbor rather than two separate devices. Option A is incorrect as FortiGate typically does not participate in STP calculations. Option B is incorrect because this " duplicate " root behavior is the expected sign of acorrectlyfunctioning MCLAG control plane. Option D is incorrect as STP remains active to prevent loops elsewhere in the fabric; it is merely logically simplified for the MCLAG domain.