The correct answers are C, D, and E . In a Layer 3 captive or isolation network design, FortiNAC-F port2 acts as the captive network service interface. The study guide states that Layer 3 captive networks require DHCP traffic to be relayed to port2 from the captive networks, and that the FortiNAC-F interface provides DHCP, DNS, and captive portal services to hosts assigned to any captive network.

That means the firewall path between the isolation VLANs and FortiNAC-F must allow DHCP , so isolated endpoints can receive an IP address from the FortiNAC-F captive network scope; DNS , so the isolated endpoint uses FortiNAC-F as its DNS server and gets redirected correctly; and HTTP/HTTPS , so the endpoint can load the FortiNAC-F captive portal page. The guide’s browser-redirection flow confirms this sequence: the host is moved to the isolation VLAN, requests DHCP, receives FortiNAC-F as the DNS server, performs DNS lookup, and then Apache/Tomcat services present the portal content.

Option A , DDNS, is not required for captive portal operation. Option B , NTP, may be useful for endpoint time accuracy or certificate-related workflows, but it is not part of the minimum traffic required for FortiNAC-F isolation network operation.