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How to: Setup a Static IP Address on CentOS

created by BasicSysAdmin

Tags: Linux, CentOS, CentOS 6, CentOS 6.5, CentOS 7

Jun 18, 2016

Introduction

This guide will show you how you can setup a static IP address on CentOS. To do this, you will need to have a basic understanding of networking.

Prerequisites

In order to follow this tutorial, you will need the following

  • Sudo Privileges

  • Basic understanding of Networking


  • Disabling Network Managers

    The first thing we are going to be doing is to stop the Network manager from trying to automatically handle the network for us. This will stop all of our settings been overridden at a later date. To do this, we can type
    sudo service NetworkManager stop

    After this, we will permanently turn this off and stop it been enabled again on startup.
    sudo chkconfig NetworkManager off

    Viewing Current Network Info

    As your adapter may be named something differently and you may also want to check on your current network setup, you should use this command.
    ip addr

    Here you can see the adapter name and the current IP.

    Editing Config File

    Before we edit the config file, you should make sure that you are editing the correct one. You can view the available files to edit using this command
    ls /etc/sysconfig/network-scripts/

    You should look for a file which is ifcfg- followed by the adapter name seen when you did the ip addr command.

    Once we have done this, we can go through and edit the configuration file for the network adapter so that we can tell it which address to use. Make sure to use the correct file which was identified in the previous step. If you get an error about nano not been installed, follow this guide

    sudo nano /etc/sysconfig/network-scripts/ifcfg-enp0s3

    This file should look a little something like this:

    You will need to alter the line highlighted to read
    BOOTPROTO="static"

    Once we have done this, we can set up our new IP at the bottom of the file. To do this, you will need to add the following three lines but make sure to put in the information which is appropriate to your network configuration.

    IPADDR=10.0.0.81 #The new ip you would like to use
    GATEWAY=10.0.0.1 #The ip of your router
    NETMASK=255.255.255.0 #The subnet mask which is normally 255.255.255.0


    When updated, this should look like this:

    You can now save (Ctrl + O and then Enter) and exit (Ctrl + X)

    Updating Gateway and NameServers

    We are now just going to add the gateway to another network config file just to make sure the system knows where to send the data when connecting to the web.
    sudo nano /etc/sysconfig/network

    In this, we just need to add the following:
    GATEWAY=10.0.0.1 #Your gateway

    Once you have done this, saved and closed the file, we can go to add the name servers we would like to use to resolve dns. The file we will need to edit is
    sudo nano /etc/resolv.conf

    You can clear the current file and enter the following
    nameserver 8.8.8.8 #Your first nameserver
    nameserver 8.8.4.4 #Your second nameserver

    You can add as many nameservers as you would like. Again, save and close this file.

    Once we have done all this, everything should be done
    Restarting Network Adapter and Testing

    We can now restart our network interface to make sure our changes have been taken into account.
    sudo systemctl restart network

    We can then also ping google to make sure we have network connectivity and that our namesevers are working.
    ping google.com

    If you go ahead and restart your server, you should see that everything is still working and using the details you used. If this is not the case, please make sure you follow the first few steps to disable the NetworkManager.