Interface configuration files control the software interfaces for individual network devices. As the system boots, it uses these files to determine what interfaces to bring up and how to configure them. These files are usually named ifcfg-name, where the suffix name refers to the name of the device that the configuration file controls. By convention, the ifcfg file's suffix, ethX, is the same as the string given by the DEVICE directive in the configuration file itself.

To configure an interface with static network settings using ifcfg files, for an interface with name eth0, create a file with name ifcfg-eth0 in the /etc/sysconfig/network-scripts/ directory as follows:

DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
NETMASK=255.255.255.0
IPADDR=10.0.1.27
NM_CONTROLLED=no

Optionally specify the hardware or MAC address using the HWADDR directive. Note that this will influence the device naming procedure as explained in Chapter 8, Consistent Network Device Naming. You do not need to specify the broadcast address as this is calculated automatically by ipcalc.

To configure an interface with dynamic network settings using ifcfg files, for an interface with name em1, create a file with name ifcfg-em1 in the /etc/sysconfig/network-scripts/ directory as follows:

DEVICE=em1
BOOTPROTO=dhcp
ONBOOT=yes
NM_CONTROLLED=no

Optionally specify the hardware or MAC address using the HWADDR directive. Note that this will influence the device naming procedure as explained in Chapter 8, Consistent Network Device Naming. You do not need to specify the broadcast address as this is calculated automatically by ipcalc.

For a listing of the configurable parameters in an Ethernet interface configuration file see the Fedora 20 System Administrator's Reference Guide.