1) Interface configuration using DHCP service example:

#vim /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=dhcp
HWADDR= 00-19-DB-AD-19-99
ONBOOT=yes

2) Interface configuration using manually set parameters:

#vim /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
HWADDR= 00-19-DB-AD-19-99
IPADDR=192.168.1.2
NETMASK=255.255.255.0
BROADCAST=192.168.1.255

GATEWAY=192.168.1.1

ONBOOT=yes
DNS1=8.8.8.8
DNS2=8.8.4.4

To check the interface configuration:

ifconfig eth0

To check the routes:

netstat -r

To restart the interface and to apply the new settings:

ifdown eth0 - disable
ifup eth0 - enable