IP address assignment with relay agent information option

Option 82 (DHCP relay information option) helps protect the FortiGate against attacks such as spoofing (or forging) of IP and MAC addresses, and DHCP IP address starvation.

The following CLI variables are included in the config system dhcp server > config reserved-address command:

circuit-id-type {hex | string}

DHCP option type; hex or string (default).

circuit-id <value>

Option 82 circuit ID of the client that will get the reserved IP address.

Format: vlan-mod-port

  • vlan: VLAN ID (2 bytes)
  • mod: 1 = snoop, 0 = relay (1 byte)
  • port: port number (1 byte)