By default, upon installation, any Linux system uses DHCP  for its network configuration. This implies that it automatically obtains an IP address from a router or a DHCP server in a network.  However, there are certain instances that require configuration of a static IP.  A good example is where you have a server, e.g a web server or an  FTP server. You definitely don’t want its IP to keep changing once the DHCP lease time is over. This will definitely cause loss of service once the IP changes.

Let’s see how we can configure a static IP  in different distros.

Configuring a static IP in Fedora 27, CentOS and RHEL 7

Firstly, list the IP of all interfaces

ifconfig -a

Sample Output

[root@localhost ~]# ifconfig -a
enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.43.160  netmask 255.255.255.0  broadcast 192.168.43.255
        inet6 fe80::fc3c:1bfc:d5c7:9bd8  prefixlen 64  scopeid 0x20
        ether 08:00:27:1d:2a:e1  txqueuelen 1000  (Ethernet)
        RX packets 1828  bytes 145269 (141.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 477  bytes 78999 (77.1 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Above, we can observe that our IP address is 192.168.43.160 and netmask is 255.255.255.0 We are going to configure this statically.

Navigate to the following path to view interface statistics of interface enp0s3

vi /etc/sysconfig/network-scripts/ifcfg-enp0s3

The sample output should contain the following parameters:

NETWORKING=yes

This tells the system to start networking service at boot time.

DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes

To set a static IP, modify the following settings:

HWADDR=08:00:27:1d:2a:e1 
TYPE=Ethernet
BOOTPROTO=none
# Server IP #
IPADDR=192.168.43.160
# Subnet #
NETMASK=255.255.255.0
# Set default gateway IP #
GATEWAY=192.168.43.1
# Set dns servers #
DNS1=192.168.43.1
DNS2=8.8.8.8
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
# Disable ipv6 #
IPV6INIT=no
NAME=enp0s3
UUID=41171a6f-bce1-44de-8a6e-cf5e782f8bd6
DEVICE=eth0
ONBOOT=yes

Restart the networking service

systemctl restart network

Verify the settings.

 ifconfig

Also, check the nameservers

cat /etc/resolv.conf

Output

# Generated by NetworkManager
nameserver 192.168.43.1
nameserver 8.8.8.8

using nmtui utility

nmtui, short for Network Manager Text User interface is a GUI tool that painlessly allows you to configure your network interface without having to touch the command line. It can be installed both on RPM and Debian based distributions.

For Centos & RHEL 7

yum install NetworkManager-tui

dnf install NetworkManager-tui  For Fedora 21 and later

Launching nmtui

nmtui

Select an interface to configure

Press ‘Tab’ key to navigate to the other options. Hit edit.

Navigate to IPV4 and select ‘show’

Hit Okay. Go back and select Quit

Finally, restart networking service.

Configuring a static IP in Ubuntu 14.04, 16.04

Navigate to the network interface configuration file

 nano /etc/sysconfig/interfaces

DHCP settings

auto eth0
iface eth0 inet dhcp

To configure a static IP, remove DHCP and append ‘static’ to ‘inet’ and enter your preferred address, netmask, gateway and dns-name servers

auto eth0
iface eth0 inet static
address 192.168.43.17
netmask 255.255.255.0
gateway 192.168.43.1
dns-nameservers 192.168.43.1 8.8.8.8

Restart networking

ifdown eth0

ifup eth0

Verify the settings using ifconfig command and cat /etc/resolv.conf

Wrapping up

Your thoughts about this article are highly welcome. Feel free to get back to us for any clarifications.