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.
The firewall DHCP Client operates
in the following manner:
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.