Networking: Configuring IP Addresses and Subnets

Mastering Networking with Linux Bash: Configuring IP Addresses and Subnets

When working with Linux systems, especially in server environments, configuring network settings such as IP addresses and subnets is a fundamental skill. Let’s explore how to manage these configurations effectively using Linux Bash, covering different package managers and distributions.

Understanding IP Addresses and Subnets

Before diving into configurations, it's vital to understand what IP addresses and subnets are. An IP address is a unique address that identifies a device on the internet or a local network. The subnet mask, on the other hand, defines the network portion of an IP address, allowing the possibility to differentiate the network segment, the device is on, from other devices.

Pre-Requisite Tools

To manage our network configurations from the command line, we need the appropriate tools installed on our Linux system. The most common tool for this task under modern Linux distributions is ip, part of the iproute2 package. Here's how to ensure it's installed on your Linux distribution:

Debian/Ubuntu (using apt)

sudo apt update && sudo apt install iproute2

Fedora (using dnf)

sudo dnf install iproute2

openSUSE (using zypper)

sudo zypper install iproute2

With the iproute2 package installed, we can start configuring our network settings.

Configuring IP Address with ip Command

To configure an IP address on a Linux system, you primarily use the ip command followed by addr and add keywords.

1. Check current IP configurations

First, check your current IP configuration with:

ip addr show

2. Assign a new IP address

Specify the IP address and the subnet mask. For instance, to set the IP address 192.168.1.100 with a subnet mask of 255.255.255.0 on eth0, you would use:

sudo ip addr add 192.168.1.100/24 dev eth0

This command sets the IP address and the /24 indicates the subnet mask.

3. Verify the changes

Verify that the IP was added:

ip addr show eth0

Persistent Network Configuration

The above method sets the IP address temporarily. It will revert after a reboot. To make it permanent, you have to edit network configuration files, which vary by distribution.

Debian/Ubuntu

On Debian-based systems, edit the /etc/network/interfaces file:

sudo nano /etc/network/interfaces

Add the following lines to set the static IP:

auto eth0
iface eth0 inet static
address 192.168.1.100
netmask 255.255.255.0
gateway 192.168.1.1

Fedora

For Fedora, the configuration files are found under /etc/sysconfig/network-scripts/. Edit the script for your interface, typically named ifcfg-eth0:

sudo nano /etc/sysconfig/network-scripts/ifcfg-eth0

Configure the script like so:

TYPE=Ethernet
BOOTPROTO=none
DEFROUTE=yes
IPADDR=192.168.1.100
PREFIX=24
GATEWAY=192.168.1.1
DEVICE=eth0
ONBOOT=yes

openSUSE

On openSUSE, use Wicked, which is a network management suite:

sudo nano /etc/sysconfig/network/ifcfg-eth0

Add these lines:

BOOTPROTO='static'
IPADDR='192.168.1.100/24'
STARTMODE='auto'

Conclusion

Understanding and configuring IP addresses and subnets on various Linux distributions is crucial for effective network management. Whether it's a temporary change with ip command or a permanent setup via configuration files, Linux offers the flexibility needed for efficient network administration. Always ensure that you have backups of configuration files before you make changes to prevent downtime due to misconfiguration.

Happy networking! 🌐