Enable IGMP snooping proxy (C): To reduce the number of unwanted IGMP reports processed by the IGMP querier, enabling IGMP snooping proxy is effective. This feature acts as an intermediary between multicast routers and hosts, optimizing the management of IGMP messages by handling report messages locally and reducing unnecessary IGMP traffic across the network. This minimizes the processing load on the IGMP querier and improves overall network efficiency.

According to theFortiSwitchOS 7.6 Administration Guideand theFortiLink 7.6 Study Guide, DHCP snooping is a security feature that prevents rogue DHCP servers from distributing incorrect IP addresses on a network.
Once enabled for a specific VLAN, the switch differentiates betweentrustedanduntrustedports to regulate DHCP traffic.
* Trusted Ports and DHCP Replies (Option A):In a managed FortiSwitch environment, all ports areuntrusted by default. To allow a DHCP server (such as a FortiGate or an external server) to provide IP addresses, the administrator must explicitly set the connecting port astrusted. DHCP snooping validates incoming packets; it allowsDHCP server messages(such as DHCPOFFER and DHCPACK) only on these trusted ports. Any DHCP server reply arriving on an untrusted port is identified as coming from a potentially rogue source and is discarded by the switch.
* Option 82 Data Insertion (Option C):FortiSwitch supportsDHCP Option 82(also known as the Relay Information Option), which provides additional security by appending location-specific information (such as the Circuit ID and Remote ID) toDHCP request packets. When DHCP snooping is active, the switch can be configured to insert this data into client requests as they enter untrusted ports. This allows the upstream DHCP server to identify the specific physical port or VLAN from which the request originated, even if the server is located in a different subnet.
Regarding the incorrect options:Option Bis false as DHCP snooping only inspects and filters DHCP-specific traffic, not general unicast data.Option Dis incorrect because DHCP requests (client-to-server) are generally permitted on all ports to ensure clients can find a server, though some configurations allow dropping requests from untrusted sources if they do not meet specific security criteria.

It provides benefits that can be obtained when using 802.1X authentication (C): MAC, IP, and protocol-based VLANs on FortiSwitch are beneficial in network environments where additional granularity is needed in traffic segmentation and security, similar to what can be achieved through 802.1X authentication. These VLAN types allow for dynamic assignment of ports to VLANs based on the characteristics of the incoming traffic, enhancing both security and network efficiency.

The native VLAN is implicitly part of the allowed VLAN on the port (C): On a managed FortiSwitch port, the native VLAN, which is the VLAN assigned to untagged traffic, is implicitly included in the list of allowed VLANs. This means it does not need to be explicitly specified when configuring VLAN settings on the port.
This configuration simplifies VLAN management and ensures that untagged traffic is handled correctly without additional configuration steps.

According to theFortiOS 7.6 Administration Guideand theFortiSwitch 7.6 FortiLink Guide, deploying managed switches over a Layer 3 underlay-such as the public internet-requires a specific tunneling mechanism to bridge Layer 2 broadcast domains. Traditional FortiLink relies on a direct Layer 2 connection; however, for remote sites,FortiLink over VXLANis the standard solution.
* FortiLink over VXLAN (Option A):Virtual Extensible LAN (VXLAN) is used to encapsulate Layer 2 Ethernet frames into Layer 3 UDP packets, allowing VLAN-tagged traffic to traverse an ISP ' s routable network. This enables the FortiGate to manage remote FortiSwitch " islands " as if they were locally connected, maintaining full VLAN segmentation across the WAN.
* Layer 3 Termination (Option E):The FortiGate acts as theVirtual Tunnel Endpoint (VTEP). It must have a reachable Layer 3 interface (such as a WAN port with a public IP or an IPsec tunnel interface) to terminate the VXLAN overlay. Once the VXLAN tunnel is terminated at the FortiGate, the encapsulated VLAN traffic is extracted, and the FortiGate can perform inter-VLAN routing and security inspection.
Regarding the incorrect options:Option Bis incorrect because the FortiGate at the central site handles the routing, eliminating the need for a local L3 device.Option Cis a performance consideration but not a functional requirement for basic connectivity.Option Dis often used for security to encrypt the underlay, but IPsec alone does not provide the Layer 2 extension capabilities required for VLAN segmentation; VXLAN is the specific component that handles the MAC-in-UDP encapsulation.