To enable a firewall interface to transmit DHCP messages between clients and servers, you must configure the firewall as a DHCP relay agent. The interface can forward messages to a maximum of eight external IPv4 DHCP servers and eight external IPv6 DHCP servers. A client DHCPDISCOVER message is sent to all configured servers, and the DHCPOFFER message of the first server that responds is relayed back to the requesting client.
You can configure a combined total of 500 DHCP servers (IPv4) and DHCP relay agents (IPv4 and IPv6) on a firewall.
Before configuring a DHCP relay agent, make sure you have configured a Layer 3 Ethernet or Layer 3 VLAN interface, and the interface is assigned to a virtual router and a zone.
Configure an Interface as a DHCP Relay Agent
Select DHCP Relay. Select Network > DHCP > DHCP Relay.
Specify the IP address of each DHCP server with which the DHCP relay agent will communicate. In the Interface field, select from the drop-down the interface you want to be the DHCP relay agent. Select either IPv4 or IPv6, indicating the type of DHCP server address you will specify. If you checked IPv4, in the DHCP Server IP Address field, click Add. Enter the address of the DHCP server to and from which you will relay DHCP messages. If you checked IPv6, in the DHCP Server IPv6 Address field, click Add. Enter the address of the DHCP server to and from which you will relay DHCP messages. If you specify a multicast address, also specify an outgoing Interface. ( Optional ) Repeat Steps 2-4 to enter a maximum of eight DHCP server addresses per IP address family.
Save the configuration. Click OK and Commit the change.

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