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Md Mohiuddin
Md Mohiuddin

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🌐 Networking Fundamentals Every DevOps Engineer Should Know (IP, DNS & Ports)

#devops #infrastructure #networking

If you're learning DevOps, networking is not optional.

Every SSH connection, web request, Docker container, Kubernetes service, and cloud resource relies on networking behind the scenes.

When applications fail to communicate, deployments break, or services become unreachable, networking is often the first place engineers investigate.

In this article, I'll cover:

✅ What IP addresses are
✅ Public vs Private IPs
✅ Understanding Subnets and CIDR
✅ How DNS works
✅ Common DNS record types
✅ Understanding Ports
✅ The Client-Server Model
✅ Useful networking commands for troubleshooting

Let's dive in.

Why Networking Matters in DevOps

Almost every modern DevOps tool depends on networking.

Examples include:

  • SSH connections to servers
  • Web applications communicating with databases
  • Docker containers talking to each other
  • Kubernetes services routing traffic
  • CI/CD pipelines deploying applications
  • Cloud services communicating across regions

When something stops working, one of the first questions engineers ask is:

Is this a networking problem?

Understanding networking helps you answer that question quickly.

What Is an IP Address?

An IP (Internet Protocol) address is a unique identifier assigned to a device on a network.

It allows devices to locate and communicate with each other.

Example IPv4 address:

192.168.1.10
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IPv4 addresses contain four numbers separated by dots.

Each section ranges from:

0 - 255
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Without IP addresses, computers wouldn't know where to send data.

Public vs Private IP Addresses

There are two major categories of IP addresses.

Public IP

A public IP address is reachable from anywhere on the internet.

Examples:

  • Cloud servers
  • Public websites
  • Home internet routers

Your AWS EC2 instance will typically have a public IP so you can SSH into it remotely.

Private IP

Private IP addresses are only accessible within a local network.

Common private ranges:

10.0.0.0 – 10.255.255.255

172.16.0.0 – 172.31.255.255

192.168.0.0 – 192.168.255.255
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You'll frequently encounter these ranges when working with:

  • AWS VPCs
  • Docker networks
  • Kubernetes clusters
  • Internal company networks

Localhost (Loopback Address)

A special IP address always refers to the current machine:

127.0.0.1
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You'll often see:

localhost
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which resolves to:

127.0.0.1
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This allows you to test applications running on your own computer without using an external network.

Understanding Subnets

As networks grow, they are divided into smaller logical sections called subnets.

A subnet helps organize devices and control traffic efficiently.

CIDR Notation

Subnets are usually written using CIDR notation:

192.168.1.0/24
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The /24 indicates the network portion of the address.

A /24 subnet provides:

256 IP addresses
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from:

192.168.1.0
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to:

192.168.1.255
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Examples:

CIDR Approx. Addresses
/16 65,536
/24 256
/28 16

You'll see CIDR blocks frequently when creating cloud networks and VPCs.

What Is DNS?

Humans prefer names.

Computers prefer IP addresses.

DNS (Domain Name System) translates domain names into IP addresses.

For example:

google.com
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becomes something like:

142.250.xxx.xxx
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This allows your browser to find the correct server.

How DNS Resolution Works

When you visit a website:

google.com
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the lookup process generally follows these steps:

Your Device
      ↓
DNS Resolver
      ↓
Root Servers
      ↓
TLD Servers (.com)
      ↓
Authoritative DNS Server
      ↓
IP Address Returned
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Finally, your computer connects to the returned IP address.

This entire process usually takes only milliseconds.

Common DNS Record Types

Record Purpose
A Domain → IPv4 Address
AAAA Domain → IPv6 Address
CNAME Domain Alias
MX Mail Server Records
TXT Verification & Security Records
NS Name Server Information

As a DevOps engineer, you'll regularly manage DNS records when deploying applications.

Understanding Ports

An IP address identifies a machine.

A port identifies a service running on that machine.

Think of it like:

IP Address = Building Address
Port = Apartment Number
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Multiple applications can run on the same server because each listens on a different port.

Common Ports Every DevOps Engineer Should Know

Port Service
22 SSH
53 DNS
80 HTTP
443 HTTPS
3306 MySQL
5432 PostgreSQL
6379 Redis
27017 MongoDB

Examples:

192.168.1.10:22
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SSH service

192.168.1.10:80
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Web server

192.168.1.10:443
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Secure website

The Client-Server Model

Most applications follow the client-server model.

A client sends a request.

A server receives the request and returns a response.

Example:

CLIENT                     SERVER

Browser  ───── Request ───► Nginx

Browser ◄──── Response ─── Nginx
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Examples of clients:

  • Web browsers
  • Mobile apps
  • curl
  • API consumers

Examples of servers:

  • Nginx
  • Apache
  • Node.js applications
  • Databases

Useful Networking Commands

ping

Check whether a host is reachable.

ping google.com
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Example output:

64 bytes from 142.x.x.x: time=14 ms
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Useful for:

  • Basic connectivity testing
  • Measuring latency

Stop with:

Ctrl + C
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nslookup

Perform a DNS lookup.

nslookup google.com
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Output shows the IP address associated with the domain.

dig

A more advanced DNS troubleshooting tool.

Basic lookup:

dig google.com
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Short output:

dig google.com +short
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Lookup MX records:

dig google.com MX
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View the full DNS resolution path:

dig +trace google.com
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curl

Send HTTP requests directly from the terminal.

curl https://google.com
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Show only response headers:

curl -I https://google.com
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Verbose mode:

curl -v https://google.com
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Save output to a file:

curl -o page.html https://google.com
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curl -I is one of the most useful troubleshooting commands in DevOps.

Following the Journey of a Request

Let's see what happens when you run:

curl https://google.com
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Step-by-step:

  1. DNS resolves google.com to an IP address.
  2. Your machine connects to that IP.
  3. It uses port 443 for HTTPS.
  4. A secure TLS connection is established.
  5. The HTTP request is sent.
  6. Google's server processes the request.
  7. An HTTP response is returned.
  8. curl displays the result. 
DNS
 ↓
IP Address
 ↓
Port 443
 ↓
TLS Handshake
 ↓
HTTP Request
 ↓
HTTP Response
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This flow is the foundation of nearly every web application you'll work with.

Final Thoughts

Networking is one of the most important skills in DevOps.

Understanding IP addresses, DNS, ports, and client-server communication gives you the foundation needed for cloud computing, Docker, Kubernetes, load balancers, CI/CD pipelines, and modern infrastructure.

The better you understand how systems communicate, the easier it becomes to troubleshoot real-world production issues.

If you have favorite networking commands or troubleshooting tips, feel free to share them in the comments.

Happy Learning! 🌐🚀

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