After installing Operating System the first thing come into mind, how to modify network setting of your Linux Box. Network management is really simple when it comes to CentOS/RHEL/fedora, Most of the setting is easy and simple to adjust. We need to modify few files to configure our networking, as most of the configuration kept in files.


LAB Scenario:

I have just installed one fresh system having CentOS 6.5 with basic installation.


Four Basic changes we are going to do.

1 – Host Name  =

2 – IP Address  =

3 – Gateway    =

4 – DNS   =


Before we get into setting up Linux networking on a CentOS system , First lets we see some network management commands to verify our current network configuration.


Command Explanation
Ifconfig -a This command will show current ip address and other interface-related information, with –a switch we can see all attached network interfaces of system.
Route enable you to view and change the routing information on the linux box.
System-network-config-tui Provides a menu-driven utility for network configuration

There are some additional files that you need to know, when you are configuring network interface.

File Path Explanation
/etc/sysconfig/network This file contains gateway and hostname information.
/etc/sysconfig/network-scripts This directory contains all the interface config files for your system


Display currently attached  network interfaces status with below command.

[root@CENTOS ~]#ifconfig –a

Out Put



There is no IP address assigned on “eth0”

Step -1 Change IP address on “eth0”

[root@CENTOS ~]#vi /etc/sysconfig/network-scripts/ifcfg-eth0


Above screenshot shows the current parameters in the configuration file, We will change parameters,
adding ip address and subnetmask see below:



Changes are marked with yellow box.

Now save and exit pressing “:wq” without quotes.


Step-2 Assign Gateway & Hostname

We are going to edit one file to change hostname and default gateway.

root@CENTOS ~]#vi /etc/sysconfig/network

Current Contents of ‘/etc/sysconfig/network’ file:



We need to change in this way:




Save and exit “:wq” without quotes.


Step-3 Assign DNS

[root@CENTOS ~]#vi /etc/resolv.conf

File will be empty if you didn’t configure dns server address.

Will assign our dns server address in this way:


Save and exit “:wq” without quotes.

TIP: if you want to hostname changing without restarting system, then we have to give one additional command:

“hostname DesireHostName” and relogin on the terminal see below:

[root@CENTOS ~]#hostname



Now logout and login again.

That’s all now time to restart network service to make our changes in action.

Here is command:

[root@CENTOS ~]#service network restart

Then lets again put ifconfig –a command to verify our network changing is take effect or not.ifconfig_linux



Step 4: Lets verify internet access on our linux box.

[root@CENTOS ~]#ping


Here we go… we are able to reach on internet ….


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