You ' ve configured the FortiLink interface, and the DHCP server is enabled by default.

The DHCP configuration shows:

set vci-match enable

set vci-string " FortiSwitch " " FortiExtender "

What this means

VCI = Vendor Class Identifier (DHCP option 60)

When vci-match is enabled, the DHCP server will only respond to DHCP requests from clients whose VCI string matches the configured vendor identifiers.

FortiSwitch and FortiExtender both send DHCP option 60 with:

" FortiSwitch "

" FortiExtender "

This is used in FortiLink deployments so only these devices receive IP addresses on the FortiLink network.

Therefore:

C. To connect, devices must match the VCI string; otherwise, they will not receive an IP address.

✔Correct.

This perfectly matches FortiGate FortiLink DHCP behavior.

Summary of incorrect options

A — Ignore FortiSwitch/FortiExtender

❌Opposite behavior.

B — Restrict based on hostname

❌VCI does NOT check hostname.

D — Reserve IPs

❌No reservation occurs; it ' s filtering, not reserving.