Networking is one of the most important foundations for anyone learning DevOps. Whether you’re working with servers, containers, cloud platforms, or automation tools, everything relies on systems communicating with each other correctly.

This post is a simple, beginner-friendly guide covering the essential networking concepts I learned early in my DevOps journey. By the end, you’ll understand IP addressing, subnets, DNS, ports, routing, SSH, and common Linux networking tools.

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1. What Is Networking?

Networking is the practice of connecting devices so they can share information. Every time you browse a website, access a server, or deploy an application, networking is involved.

Different types of networks serve different purposes:

Type	Description	Example
LAN	Covers a small area	Home Wi-Fi, office network
MAN	Covers a city-sized area	City-wide fiber or Wi-Fi
WAN	Connects networks across long distances	The Internet

Even large cloud providers like Azure, AWS and Google Cloud are built on top of massive WAN infrastructures.

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2. IP Addressing

Every device on a network has an IP address. It acts like a home address: without it, data wouldn’t know where to go.

IPv4 Format

IPv4 addresses are written in four sections:

192.168.1.10

Each IP contains:

• Network ID – identifies the network
• Host ID – identifies the device inside that network

Although older systems used fixed “classes” (Class A, B, C), modern networks rely on CIDR notation for flexibility.

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3. CIDR and Subnetting

Subnetting is the process of dividing a network into smaller parts. DevOps engineers work with subnets all the time in cloud environments like AWS VPCs or when designing Docker/Kubernetes networks.

CIDR Basics

CIDR notation looks like this:

10.0.0.0/24

The number after the slash tells you how many bits belong to the network. The rest are for hosts.

Example:

• /24 → 24 bits for network, 8 bits for hosts
• Host capacity → 2^8 = 256 total IPs (254 usable)

Subnetting Example

If you divide a /24 network into four equal networks:

• You borrow 2 bits
• New CIDR becomes /26
• Each subnet has 64 IP addresses

Another Example: Divide 10.0.0.0/24 Into 8 Subnets

Borrow 3 bits:

2^3 = 8 subnets

Each subnet becomes /27.

This level of subnetting is common when organizing infrastructure into dev, staging, and production networks.

If you want to check your work, the ipcalc tool helps:

ipcalc 192.168.10.0/26

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4. DNS: Turning Names Into IPs

Computers communicate using IP addresses, but humans remember names. DNS (Domain Name System) converts readable names like:

google.com

into machine-friendly IP addresses.

How DNS Resolution Works

1. You enter a domain in your browser.
2. Your computer checks its local DNS cache.
3. If it’s not found, it asks a DNS resolver (like 8.8.8.8).
4. The resolver contacts DNS servers to find the IP.
5. The IP is returned to your system.
6. Your computer connects to the website.

Useful commands:

dig google.com
nslookup google.com

In DevOps, DNS issues often cause “site not reachable” or “service can’t connect” errors.

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5. Ports and Protocols

An IP address can host many services. Ports help differentiate them.

Examples:

• 22 → SSH
• 80 → HTTP
• 443 → HTTPS
• 53 → DNS
• 3306 → MySQL

TCP vs UDP

• TCP is reliable and connection-oriented (used for SSH, HTTPS, APIs).
• UDP is faster but connectionless (used for DNS, streaming, VoIP).

Check open ports:

ss -tuln

Or test a web server:

curl -I https://example.com

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6. Routing and Gateways

A gateway is the device that forwards your traffic to other networks. On home networks, your router serves that role.

View your routing table:

ip route show

You will usually see a line like:

default via 192.168.1.1

This means anything not on your local network goes through the router.

To see how your packet travels to a website:

traceroute google.com

This helps diagnose slow or failing network paths.

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7. Essential Linux Networking Tools

These commands are used daily by DevOps engineers to diagnose issues.

Command	Purpose
ping	Test basic connectivity
traceroute	See the path traffic takes
curl	Make HTTP requests
ss / netstat	Check open ports and connections
dig / nslookup	Inspect DNS
telnet or nc	Test if a port is open

Examples:

ping google.com
curl -I https://google.com
telnet google.com 443

Understanding these tools makes network debugging much easier.

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8. SSH: Secure Remote Access

SSH (Secure Shell) is how DevOps engineers connect to remote Linux servers.

Basic usage:

ssh user@server_ip

SSH encrypts all traffic and is far safer than older remote-login methods.

SSH Keys

SSH keys allow password-less authentication.

Generate keys:

ssh-keygen

Upload the public key:

ssh-copy-id user@server_ip

Most cloud platforms (AWS, DigitalOcean, Azure) depend heavily on SSH keys for secure access.

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9. A Small Practice Lab (Optional)

Try these on your system:

1. Find your IP and default gateway
2. Use ping, curl, and traceroute on any website
3. Use dig to look up the IP of a domain
4. SSH into a local VM or server
5. Subnet 10.0.0.0/24 into 8 subnets
6. Describe what happens when you run:

ping google.com

Hands-on practice will cement your understanding.

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Final Thoughts

Networking isn’t just “another topic” in DevOps—it’s the foundation everything else sits on. You’ll need it when working with Docker, Kubernetes, cloud networking (AWS VPCs), load balancers, service discovery, firewalls, and CI/CD pipelines.

You now understand the essentials:

• What networks are and how devices communicate
• How IP addresses and subnets work
• Why DNS is critical
• How ports enable multiple services
• How routing moves traffic
• How to test and troubleshoot connectivity
• How to access servers using SSH

Master these fundamentals and you’ll be ready to tackle more advanced DevOps networking topics like load balancing, NAT, container networking, and Kubernetes networking.