Setting IP Address on CentOS

Introduction

Configuring an IP address on a CentOS server is one of the basic tasks in Linux server administration. An IP address allows the server to communicate with other devices on a network and access the internet. CentOS supports both dynamic IP addresses using DHCP and static IP addresses configured manually.

This guide explains how to set a static IP address on CentOS using the command line.

Why Use a Static IP Address?

A static IP address is recommended for servers because it provides a permanent network address. This is useful for:

Web servers
Database servers
File sharing systems
Remote SSH access
Hosting services

Unlike DHCP, a static IP address does not change automatically.

Checking Network Interfaces

Before configuring the IP address, check the available network interfaces.

Use the following command:

ip addr

Example output:

2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP>

In this example, ens33 is the network interface name.

Configuring a Static IP Address

Open the network configuration file:

sudo nano /etc/sysconfig/network-scripts/ifcfg-ens33

Example configuration:

TYPE=Ethernet

BOOTPROTO=none

NAME=ens33

DEVICE=ens33

ONBOOT=yes

IPADDR=192.168.1.100

PREFIX=24

GATEWAY=192.168.1.1

DNS1=8.8.8.8

DNS2=8.8.4.4

Explanation:

BOOTPROTO=none disables DHCP
IPADDR sets the static IP address
PREFIX=24 defines the subnet mask
GATEWAY sets the default gateway
DNS1 and DNS2 configure DNS servers

Restarting the Network Service

After saving the configuration, restart the network service.

sudo systemctl restart NetworkManager

Or:

sudo systemctl restart network

Verifying the Configuration

Check whether the new IP address is active.

ip addr

You can also test internet connectivity:

ping google.com

If the server replies successfully, the configuration is working correctly.

Using DHCP Instead of Static IP

If you want the server to receive an IP address automatically from the router, use DHCP.

Example configuration:

BOOTPROTO=dhcp

ONBOOT=yes

This method is commonly used for personal computers or temporary environments.

Common Problems

Some common issues when configuring IP addresses on CentOS include:

Incorrect network interface name
Wrong gateway configuration
DNS server errors
Network service not restarted
Firewall restrictions

Always double-check the configuration file after editing.

Conclusion

Setting an IP address on CentOS is an important step in server configuration. Administrators can choose between static IP and DHCP depending on their needs. Static IP addresses are recommended for production servers because they provide stable and reliable network connectivity.

With proper configuration, CentOS servers can communicate efficiently across local networks and the internet.