The firewall can function as a DHCP server and as a DHCP client. Dynamic Host Configuration Protocol, RFC 2131, is designed to support IPv4 and IPv6 addresses. The Palo Alto Networks implementation of DHCP server supports IPv4 addresses only.
The firewall DHCP server operates in the following manner:
When the DHCP server receives a DHCPDISCOVER message from a client, the server replies with a DHCPOFFER message containing all of the predefined and user-defined options in the order they appear in the configuration. The client selects the options it needs and responds with a DHCPREQUEST message.
When the server receives a DHCPREQUEST message from a client, the server replies with its DHCPACK message containing only the options specified in the request.
When the DHCP client receives a DHCPOFFER from the server, the client automatically caches all of the options offered for future use, regardless of which options it had sent in its DHCPREQUEST.
By default and to save memory consumption, the client caches only the first value of each option code if it receives multiple values for a code.
There is no maximum length for DHCP messages unless the DHCP client specifies a maximum in option 57 in its DHCPDISCOVER or DHCPREQUEST messages.