Chapter 12 Dynamic Host Configuration Protocol (Dhcp); Why Use Dhcp; Configuring A Dhcp Server - Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Manual

Section 12.2:Configuring a DHCP Server 121
12 Dynamic Host Configuration Protocol
(DHCP)
Dynamic Host Configuration Protocol (DHCP) is network protocol for automatically assigning
TCP/IP information to client machines. Each DHCP client connect to the centrally-located DHCP
server that returns the client's network configuration including IP address, gateway, and DNS servers.

12.1 Why Use DHCP?

DHCP is useful for fast delivery of client network configuration. When configuring the client system,
the administrator can choose DHCP and not have to enter an IP address, netmask, gateway, or DNS
servers. The client retrieves this information from the DHCP server. DHCP is also useful if an admin-
istrator wants to change the IP address of a large number of systems. Instead of reconfiguring all the
systems, he can just edit one DHCP configuration file on the server for the new set of IP address. If
the DNS servers for an organization changes, the changes are made on the DHCP server, not on all the
DHCP clients. Once the network is restarted on the clients (or the clients are rebooted), the changes
will take effect.
Furthermore, if a laptop or any type of mobile computer is configured for DHCP, it can be moved from
office to office without having to reconfiguring it as long as each office has a DHCP server that allows
it to connect to the network.

12.2 Configuring a DHCP Server

You can configure a DHCP server using the configuration file /etc/dhcpd.conf.
DHCP also uses the file /var/lib/dhcp/dhcpd.leases to store the client lease database. Re-
fer to Section 12.2.2, Lease Database for more information.
12.2.1 Configuration File
The first step in configuring a DHCP server is to create the configuration file that stores the network
information for the clients. Global options can be declared for all clients, or options can be declared
for each client system.
The configuration file can contain any extra tabs or blank lines for easier formatting. The keywords
are case-insensitive, and lines beginning with a hash mark (#) are considered comments.
There are two types of statements in the configuration file: