Enhancing IPsec security using EMS SN verification 7.4.4
This feature ensures that only licensed FortiClient endpoints can establish an IPsec VPN connection with FortiGate. The FortiGate performs EMS SN verification, and for this feature to work, both the FortiGate and FortiClient endpoints must be connected to the same FortiClient EMS.
For more information about this feature, see Enhancing IPsec security and performance.