Technical Tip: How to disable DHCP lease time on FortiGate

DHCP lease time is the duration for which a DHCP server assigns an IP address to a client. Once the lease time expires, the IP address is released and can be reassigned to another client. The lease time is measured in seconds and can be configured on the DHCP server. The DHCP lease time can be adjusted based on network requirements.

By default, FortiGate sets the lease time to 7 days (604,800 seconds), with a maximum of 10 days (864,000 seconds). In environments where clients connect and disconnect frequently, such as guest or wireless networks, shorter lease times are recommended to allow IP addresses to be reused more efficiently.

Refer to the steps below to disable the DHCP lease time in the CLI. Setting the value to 0 will disable the lease time.

config system dhcp server

    edit 1

        set lease-time 0

end

Verify the lease time is disabled in the GUI:

Related article:
Technical Tip: How to configure FortiGate as DHCP server