In the FortiSASE architecture, Network Lockdown is a security feature designed to prevent off-net (off-fabric) endpoints from accessing the internet or local network without the protection of the SASE security stack.

Triggering Lockdown: When an endpoint is determined to be " off-net " —meaning it does not satisfy the on-net rule sets defined in its endpoint profile—a timer starts for a configurable grace period .

Function of the Grace Period: During this period, the endpoint maintains full access to the LAN and the internet. 4 The specific purpose of this grace period is to provide the user with a window of time to attempt a connection to the FortiSASE VPN tunnel or an alternate corporate tunnel. 5 This ensures that users can authenticate and regain a secure " on-net " status before any connectivity restrictions are enforced.

Enforcement: If the grace period expires and the endpoint has failed to establish a VPN connection, FortiClient enforces a strict lockdown. 7 In this state, the device cannot reach the LAN or the internet, except for specifically defined " Exempt Destinations " (such as captive portal login pages or the FortiSASE portal itself).

Resetting the Timer: Any attempt to connect to the tunnel during the grace period resets the timer, providing additional opportunities for the user to remediate their connection status. 8

According to the FortiSASE 25 Administrator Study Guide , the grace period is an essential user-experience setting that balances strict " zero-trust " security with the practical need for users to access the network briefly to establish their secure tunnel.