You have installed CentOS and now you’d like to either change the IP address or add additional LAN cards (NIC). There are a couple of ways to configure the network card using the command line but only some commands will take immediate effect on kernel.

Configure network with immediate effect

Using a single command line to configure the network

# ifconfig eth0 192.168.0.10 netmask 255.255.255.0

[or]

# ip addr add 192.168.0.10 dev eth0

Configure network with setup or netconfig

If you are using netconfig (or) setup utility it will only overwrite the /etc/sysconfig/network-scripts/ifcfg-eth0 file. Then , after that u have to restart the network service like follow,

# setup

Network configuration -> Edit Devices -> eth0 (eth0) – Intel Corporation 82540EM Gigabit Ethernet Controller

Save your settings and quit

[or]

# system-config-network

Edit Devices -> eth0 (eth0) – Intel Corporation 82540EM Gigabit Ethernet Controller

Save your settings and quit

Restart your network in order for your configuration to take effect.

# /etc/init.d/network restart

Configure network by editing configuration

Lastly you can configure the network by editing the configuration files stored in the /etc/sysconfig/network-scripts/ directory.

# cd /etc/sysconfig/network-scripts/

# vi ifcfg-eth0

Append/modify as follows:

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# Intel Corporation 82540EM Gigabit Ethernet Controller
DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
HWADDR=06:01:78:a7:00:33
NETMASK=255.255.255.0
IPADDR=192.168.0.10
TYPE=Ethernet

Save and close the file. Define default gateway and hostname in /etc/sysconfig/network configuration file

# vi /etc/sysconfig/network

Append/modify configuration as follows:

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NETWORKING=yes
NETWORKING_IPV6=no
HOSTNAME=centos.how2centos.com
GATEWAY=192.168.0.1

Save and close the file. Restart networking:

# /etc/init.d/network restart