Configuring Networking in Linux: A Guide for Red Hat and Debian-Based Systems

Introduction

Networking is at the core of any Linux server’s operation. Whether you’re setting up a web server, file share, or simply enabling internet access, configuring the network interface correctly is crucial. This guide provides a comprehensive comparison and walkthrough for setting up networking on two major Linux families:

• Red Hat-based (RHEL, CentOS, Rocky, AlmaLinux)
• Debian-based (Ubuntu, Debian)

We’ll cover both manual (CLI) and persistent (configuration file) methods, using modern tools like nmcli and netplan, with examples, flow, and common use cases.

Table of Contents

1. Understanding Linux Network Interfaces
2. Checking Network Status
3. Configuring Networking in Red Hat-Based Systems
4. Configuring Networking in Debian-Based Systems
5. Use Cases (Static IP, DHCP, Bridging, DNS)
6. Troubleshooting Tips
7. Conclusion

1. Understanding Linux Network Interfaces

In Linux, every network device is treated as a file and usually appears as:

• eth0, ens33, or enp0s3 for Ethernet
• wlan0 or wlp2s0 for wireless
• lo for loopback

Modern distributions often use Predictable Network Interface Names like enp0s3.

You can view all interfaces using:

ip a

or

nmcli device status

2. Checking Network Status

Before making changes, always verify your current setup:

ip addr show
ip route show
nmcli connection show

For DNS resolution testing:

ping google.com
cat /etc/resolv.conf

3. Configuring Networking in Red Hat-Based Linux

➤ Option 1: Using nmcli (NetworkManager CLI)

Set a static IP:

nmcli con add con-name static-eth0 ifname eth0 type ethernet ip4 192.168.1.100/24 gw4 192.168.1.1
nmcli con mod static-eth0 ipv4.dns "8.8.8.8 1.1.1.1"
nmcli con up static-eth0

Enable DHCP:

nmcli con add type ethernet con-name dhcp-eth0 ifname eth0
nmcli con up dhcp-eth0

➤ Option 2: Manual Configuration (Legacy method)

Edit the network script:

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

Example static IP config:

DEVICE=eth0
BOOTPROTO=static
IPADDR=192.168.1.100
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
DNS1=8.8.8.8
ONBOOT=yes

Then restart networking:

sudo systemctl restart network

4. Configuring Networking in Debian-Based Linux

➤ Option 1: Using netplan (Ubuntu 18.04+ and Debian 11+)

Netplan is the default network configuration tool in modern Ubuntu/Debian.

Edit or create config:

sudo vi /etc/netplan/01-netcfg.yaml

Static IP example:

network:
  version: 2
  ethernets:
    eth0:
      dhcp4: no
      addresses:
        - 192.168.1.100/24
      gateway4: 192.168.1.1
      nameservers:
        addresses: [8.8.8.8, 1.1.1.1]

Apply changes:

sudo netplan apply

➤ Option 2: Legacy /etc/network/interfaces (Debian 10 or older)

Edit:

sudo vi /etc/network/interfaces

Example static IP:

auto eth0
iface eth0 inet static
  address 192.168.1.100
  netmask 255.255.255.0
  gateway 192.168.1.1
  dns-nameservers 8.8.8.8 1.1.1.1

Restart networking:

sudo systemctl restart networking

5. Use Cases

Scenario	Recommended Method	Notes
Static IP for servers	Netplan (Debian) / nmcli (RedHat)	Easier to manage persistently
Dynamic IP for laptops	DHCP via nmcli or Netplan	Simpler setup
Bridged networking	nmcli con add type bridge	For virtualization setups
Custom DNS setup	resolv.conf, or YAML (Netplan)	For local DNS or filtering

---

6. Troubleshooting Tips

• Interface not coming up? ip link set eth0 up
• DNS not working? systemd-resolve –status cat /etc/resolv.conf
• NetworkManager errors? nmcli general logging level DEBUG journalctl -u NetworkManager
• Applying Netplan fails? netplan try

7. Conclusion

Whether you’re on Red Hat or Debian-based Linux, networking setup boils down to two key steps: configuring the interface and ensuring persistence. While the tools vary (nmcli, Netplan, legacy files), the goals remain the same: connectivity, reliability, and control.

Mastering these configuration methods is essential for:

• Virtual machines & cloud instances (AWS, GCP, Proxmox, etc.)
• Hosting web applications
• Managing servers