An administrator is configuring FortiNAC-F to manage FortiGate VPN users.

The firewall policy for an unauthorized VPN host is an isolation policy. When a remote endpoint first establishes its VPN tunnel, FortiGate assigns the client an IP address plus two DNS servers: the production DNS server as primary and the FortiNAC-F Port2 VPN-context address as secondary . Until FortiNAC-F validates the endpoint, FortiGate firewall policies restrict the client ' s traffic so that it can communicate only with the FortiNAC-F Port2 VPN interface .

This restriction deliberately prevents access to the primary production DNS server. Consequently, DNS resolution against the primary server fails and the endpoint falls back to the secondary DNS server—FortiNAC-F. FortiNAC-F then resolves the request toward its VPN isolation interface and presents the VPN captive portal . The user can subsequently run or download the required FortiNAC-F agent, allowing FortiNAC-F to perform identification and endpoint-compliance validation.

After successful authorization, FortiNAC-F sends the appropriate group/tag information to FortiGate, causing the host to match a different firewall policy that permits the required production resources and blocks the isolation interface.

Study Guide Reference: Advanced Features → FortiGate VPN Integration → VPN Host Isolation and Firewall Policies , pp. 346–354 .