User`s guide

XSR User’s Guide 295
12
Configuring DHCP
Overview of DHCP
The Dynamic Host Configuration Protocol (DHCP) allocates and delivers
configuration values, including IP addresses, to Internet hosts. Consisting of
of two components, DHCP provides host-specific configuration parameters
from a DHCP Server to a host, and allocates network addresses to hosts.
Recent extensions to the DHCP protocol extends high-availability,
authenticated and QoS-dependent configuration of Internet hosts.
DHCP is based on the client-server model - a designated DHCP Server
allocates network addresses and delivers configuration values to dynamically
configured clients. Throughout this chapter, the term server refers to a host
providing initialization values via DHCP, and the term client refers to a host
requesting initialization values from a DHCP Server.
DHCP allocates IP addresses in two ways:
 Dynamic allocation assigns an IP address to a client for a limited
interval - lease - (or until a client explicitly relinquishes its address).
 Manual allocation involves a client IP address assigned by the
network administrator, with DHCP used simply to convey the
assigned address to the client.
DHCP messages are formatted similar to BOOTP messages to capture BOOTP
Relay Agent behavior and allow existing BOOTP clients to interoperate with
DHCP servers. DHCP is backward compatible with BOOTP (RFC-951).
Implemented as an improvement to BOOTP, DHCP differs from BOOTP by
its dynamically IP address allocation and lease definition capabilities.