Cisco ASA Series User Manual

CHAPTER
1-1
Cisco ASA Series CLI Configuration Guide
1
Configuring DHCP
This chapter describes how to configure the DHCP server and includes the following sections:
• Information About DHCP, page 1-1
• Licensing Requirements for DHCP, page 1-2
• Guidelines and Limitations, page 1-2
• Configuring a DHCP Server, page 1-3
• Configuring the DHCP Relay Service, page 1-8
• Additional References, page 1-9
• DHCP Monitoring Commands, page 1-10
• Feature History for DHCP, page 1-10
Information About DHCP
The DHCP Relay Agent sends Dynamic Host Configuration Protocol (DHCP) messages between DHCP
clients and servers on different IP networks. DHCP provides network configuration parameters, such as
IP addresses, to DHCP clients. The ASA can provide a DHCP server or DHCP relay service to DHCP
clients attached to ASA interfaces. The DHCP server provides network configuration parameters
directly to DHCP clients. The DHCP relay service sends DHCP requests received on one interface to an
external DHCP server located on a different interface.
A client locates a DHCP server to request the assignment of configuration information using a reserved,
link-scoped multicast address, which indicates that the client and server should be attached to the same
link. However, in some cases where ease of management, economy, or scalability is the concern, we
recommend that you allow a DHCP client to send a message to a server that is not connected to the same
link. The DHCP relay agent, which may reside on the client network, can relay messages between the
client and server. The relay agent operation is transparent to the client.
DHCP for IPv6 (DHCPv6) specified in RFC 3315 enables IPv6 DHCP servers to send configuration
parameters such as network addresses or prefixes and DNS server addresses to IPv6 nodes (that is,
DHCP clients). DHCPv6 uses the following multicast addresses:
• All_DHCP_Relay_Agents_and_Servers (FF02::1:2) is a link-scoped multicast address used by a
client to communicate with neighboring (that is, on-link) relay agents and servers. All DHCPv6
servers and relay agents are members of this multicast group.
• The DHCPv6 relay service and server listen for messages on UDP port 547. The ASA DHCPv6 relay
agent listens on both UDP port 547 and the All_DHCP_Relay_Agents_and_Servers multicast
address.

Cisco ASA Series Specifications

General

Brand	Cisco
Model	ASA Series
Category	Network Hardware
Language	English