Troubleshooting Tip: How to fix error "Must set IPv4 or IPv6 range. object check operator error, -45, discard the setting Command fail. Return code -45"

When mode-cfg is enabled, FortiGate acts as a DHCP server for VPN clients, dynamically assigning IP addresses and other network configuration details. To avoid the error, it is essential to configure the ipv4-start-ip and ipv4-end-ip range (or the equivalent IPv6 range, if applicable).

For instance,

config vpn ipsec phase1-interface

edit <vpn tunnel>

set ipv4-start-ip X.X.X.X <- Where (X.X.X.X and Y.Y.Y.Y is starting and ending IP range).
set ipv4-end-ip Y.Y.Y.Y

end

After setting the IP range, the error should no longer appear.