20.3. Configuring a DHCP Client
The first step for configuring a DHCP client is to make
sure the kernel recognizes the network interface
card. Most cards are recognized during the installation
process and the system is configured to use the correct
kernel module for the card. If a card is added after
installation, Kudzu
[9] will recognize it and prompt you for the
proper kernel module (Be sure to check the Hardware
Compatibility List at https://hardware.redhat.com/hcl/). If
either the installation program or kudzu does not
recognize the network card, you can load the correct
kernel module (refer to Chapter 40, General Parameters and Modules for
details).
To configure a DHCP client manually, modify the /etc/sysconfig/network file to
enable networking and the configuration file for each
network device in the /etc/sysconfig/network-scripts
directory. In this directory, each device should have a
configuration file named ifcfg-eth0, where eth0 is the network device
name.
The /etc/sysconfig/network file
should contain the following line:
NETWORKING=yes
The NETWORKING variable must
be set to yes if you want
networking to start at boot time.
The /etc/sysconfig/network-scripts/ifcfg-eth0
file should contain the following lines:
DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
A configuration file is needed for each device to be
configured to use DHCP.
Other options for the network script includes:
-
DHCP_HOSTNAME
— Only use this option if the DHCP server
requires the client to specify a hostname before
receiving an IP address. (The DHCP server daemon in
Red Hat Enterprise Linux does not support this
feature.)
-
PEERDNS=<answer>,
where <answer>
is one of the following:
-
yes —
Modify /etc/resolv.conf with
information from the server. If using DHCP, then
yes is the
default.
-
no — Do
not modify /etc/resolv.conf.
-
SRCADDR=<address>,
where <address>
is the specified source IP address for outgoing
packets.
-
USERCTL=<answer>,
where <answer>
is one of the following:
If you prefer using a graphical interface, refer to Chapter 14, Network Configuration for instructions on using
the Network Administration
Tool to configure a network interface to use
DHCP.
Tip
For advanced configurations of client DHCP options such as
protocol timing, lease requirements and requests, dynamic
DNS support, aliases, as well as a wide variety of values
to override, prepend, or append to client-side
configurations, refer to the dhclient and dhclient.conf man pages.
