Dynamic Host Configuration Protocol (DHCP) Introduction
©2008 Allied Telesis Inc. All rights reserved.
52.2
AlliedWare Plus
TM
Operating System Software Reference C613-50003-00 REV E
Software Version 5.2.1
Introduction
This chapter describes the Dynamic Host Configuration Protocol (DHCP) support provided by
your device. This includes how to configure your device to:
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act as a DHCP and BOOTP server
■
act as a DHCP relay agent
■
use the DHCP client to obtain IP addresses for its own interfaces
Note that you can configure your device to operate as both a DHCP relay agent and a DHCP/
BOOTP server.
BOOTP
Bootstrap Protocol (BOOTP) is a UDP-based protocol that enables a booting host to
dynamically configure itself without external interventions. A BOOTP server responds to
requests from BOOTP clients for configuration information, such as the IP address the client
should use. BOOTP is defined in RFC 951, Bootstrap Protocol (BOOTP).
RFC 1542, Clarifications and Extensions for the Bootstrap Protocol, defines extensions to the
BOOTP protocol, including the behavior of a DHCP relay agent.
DHCP
DHCP is based on BOOTP, and is defined in RFC 2131. It extends the BOOTP mechanism by
providing:
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a method for passing configuration information to hosts on a TCP/IP network
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automatic allocation of reusable network addresses
■
other additional configuration options
When your device is configured as a DHCP server, it allocates IP addresses and other IP
configuration parameters to clients (hosts), when the client requests them. This lets you
configure your IP network without manually configuring every client. Note that each client must
also be configured to receive its IP address automatically.
As well as addresses, a DHCP server assigns a wide range of parameters to clients, including
subnet information and mask, domain and hostname, server addresses, keepalive times, MTUs,
boot settings, encapsulation settings, time settings, and TCP settings.
DHCP is designed to interoperate with BOOTP clients as well as DHCP clients, without the
BOOTP clients needing any change to their initialization software.
DHCP Relay Agents
DHCP relay agents pass BOOTP and DHCP messages between servers and clients. Networks
where the DHCP or BOOTP server does not reside on the same IP subnet as its clients need
the intermediate routers to act as relay agents.