Linux Networking Made Simple — IP, CIDR, Subnetting, nmcli/nmtui, Routes, DNS & Troubleshooting

Murali Krishna · Post by **Murali Krishna** » Sat Jun 13, 2026 11:26 am

Linux Networking Made Simple — IP, CIDR, Subnetting, nmcli/nmtui, Routes, DNS & Troubleshooting
A beginner-friendly guide explained in plain language, with real commands you can copy (AlmaLinux 9 / RHEL 9 — NetworkManager)

─────────────────────────────────────────

New to networking? Start here.
This guide explains each idea in everyday words first, then shows the exact command. No jargon dumped on you — read top to bottom and you'll be able to configure a Linux box's network with confidence.

─────────────────────────────────────────

1 IP Addressing — the basics

Think of an IP address like a home address for a computer. Just as the postman needs your house number and street to deliver mail, the network needs an IP address to deliver data to the right machine.

An IPv4 address looks like this: 192.168.1.10 — four numbers (0–255) separated by dots.

Two parts hidden inside every IP

Network part — like the street name. All devices on the same network share it.
Host part — like the house number. Unique to each device on that street.

Private addresses (used inside homes/offices, free to use)

10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.255

Everything else is a public address, used on the open internet.

Tip: Your home router almost always uses something like 192.168.0.1 or 192.168.1.1 — that's a private address.

─────────────────────────────────────────

2 CIDR — what the "/24" means

You'll often see an address written like 192.168.1.10/24. That /24 is called CIDR notation, and it simply tells you how much of the address is the "street name" (network) and how much is the "house number" (host).

Plain-language version: the number after the slash = how many bits belong to the network. The rest are free for devices.

The three you'll see most often

/24 = netmask 255.255.255.0 — up to 254 usable devices (a typical small network)
/16 = netmask 255.255.0.0 — up to 65,534 devices (a large network)
/8 = netmask 255.0.0.0 — millions of devices (very large)

Simple rule: Bigger slash number = smaller network (fewer devices). /24 is small, /8 is huge.

─────────────────────────────────────────

3 Subnetting — splitting one network into smaller ones

Imagine a big office building with one giant open floor. Subnetting is like putting up walls to make separate rooms — each department gets its own space, traffic stays organised, and you control who talks to whom.

Simple example
You have the network 192.168.1.0/24 (254 devices in one room). Split it into two smaller rooms:

192.168.1.0/25 — first half, addresses .1 to .126 (126 devices)
192.168.1.128/25 — second half, addresses .129 to .254 (126 devices)

Each /25 is a separate subnet. Adding one bit to the network part (/24 -> /25) cuts the size in half each time.

Three reserved addresses in any subnet

Network address — the first one (e.g. 192.168.1.0), names the subnet itself
Broadcast address — the last one (e.g. 192.168.1.255), "everyone on this subnet"
Gateway — usually the first usable (e.g. 192.168.1.1), the door to other networks

Why bother? Smaller subnets = less broadcast noise, better security boundaries, and tidier IP planning.

─────────────────────────────────────────

4 nmcli — configuring the network from the command line

On AlmaLinux 9, the network is managed by NetworkManager, and nmcli is its command-line tool. A "connection" is a saved profile of settings for a network card.

See what you have