DHCP Overview
DHCP is a standardized protocol defined in
RFC 2131,
Dynamic Host Configuration Protocol.
DHCP has two main purposes: to provide TCP/IP and link-layer configuration
parameters and to provide network addresses to dynamically configured
hosts on a TCP/IP network.
DHCP uses a client-server model of communication. This model
consists of three roles that the device can fulfill: DHCP client,
DHCP server, and DHCP relay agent.
A device acting as a DHCP client (host) can request an
IP address and other configuration settings from a DHCP server.
Users on client devices save configuration time and effort, and
need not know the network’s addressing plan or other resources and
options they are inheriting from the DHCP server.
A device acting as a DHCP server can service clients. By
using any of three
DHCP Addressing mechanisms,
the network administrator saves configuration time and has the benefit
of reusing a limited number of IP addresses when a client no longer
needs network connectivity. The server can deliver IP addressing
and many DHCP options to many clients.
A device acting as a DHCP relay agent transmits DHCP messages between
DHCP clients and servers.
DHCP uses
User Datagram Protocol (UDP),
RFC 768, as its transport protocol. DHCP
messages that a client sends to a server are sent to well-known
port 67 (UDP—Bootstrap Protocol and DHCP).
DHCP Messages that a
server sends to a client are sent to port 68.
An interface on a Palo Alto Networks
® firewall can
perform the role of a DHCP server, client, or relay agent. The interface
of a DHCP server or relay agent must be a Layer 3 Ethernet, Aggregated
Ethernet, or Layer 3 VLAN interface. You configure the firewall
interfaces with the appropriate settings for any combination of
roles. The behavior of each role is summarized in
Firewall as a DHCP Server and Client.
The firewall can also function as a
DHCPv6 client,
with or without prefix delegation.
The firewall supports DHCPv4 Server and DHCPv6 Relay.
The Palo Alto Networks implementation of DHCP server supports
IPv4 addresses only. Its DHCP relay implementation supports IPv4
and IPv6. DHCP client supports IPv4 and IPv6 addresses. DHCP client
is not supported in High Availability active/active mode.
