TL;DR

• Networking felt overwhelming at first like OSI, ports, DNS, traceroute… too much flying around

• EC2 + Security Groups taught me how traffic actually flows

• Fixed beginner issues like SSH key permissions, blocked ports, missing tools

• Ended the week with a clear idea of how machines talk

Why I Started With Networking

Before touching CI/CD, Docker, Kubernetes, or anything flashy, I wanted to understand the basics.
If the network layer fails, nothing else works not APIs, not deployments, not SSH, not monitoring.

So I chose to start with the fundamentals instead of blindly copying commands.

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📌 What Confused Me (and how I got unstuck)

OSI & TCP-IP Model

I didn’t get why there were so many layers. It felt unnecessary.

What helped:

• Seeing real tools mapped to layers

• Understanding that each layer has a role in how data travels

• Realizing the layers aren’t something to memorize ,they’re a mental model

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Inbound vs Outbound Traffic

I mixed these up all the time.

What finally made it click:

• Inbound = who can reach my EC2

• Outbound = where my EC2 is allowed to go

Once I saw them as “incoming door” vs “outgoing door,” Security Groups became simple.

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SSH Key Annoyances

Small issues but extremely irritating at first:

• PEM file must have strict permissions

chmod 400 key.pem

• Wrong file location → SSH breaks

• SSH just refuses if permissions are too open

• Port 22 must be open in the SECURITY GROUPS

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DNS, Dig & Traceroute

DNS felt confusing until I understood that it’s literally the internet’s phonebook.

Traceroute also looked chaotic until I focused on:

• The hop where latency spikes

• The hop where timeout begins

After that, interpreting it became easier.

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📌 What I Did This Week

1. OSI & TCP/IP

• Learned each layer’s role

• Connected tools (ping/curl/dig) to specific layers

• Stopped memorizing and started understanding

2. Protocols & Ports

• Understood why DevOps cares about specific ports

• Covered: SSH 22, HTTP 80, HTTPS 443, DNS 53, DB ports, Redis 6379

• Looked at ports used by tools like Jenkins, Kubernetes API, Prometheus, Docker registry

3. Launched EC2

• Picked Ubuntu 22.04

• t2.micro free tier

• Enabled public IP

• Created and secured PEM key

4. Configured Security Groups

• Opened port 22 for my IP

• Allowed HTTP/HTTPS

• Understood inbound/outbound behaviour

• Saw how 1 wrong SECURITY GROUP rule breaks everything

5. Networking Commands

Used practical tools instead of just reading theory:

• ping → basic connectivity

• traceroute → see the path

• ss/netstat → check listening ports

• curl → test APIs/services

• dig / nslookup → DNS behaviour

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📌 Small Beginner Issues That Took Time

These are the tiny mistakes that slow down beginners the most:

• SSH wouldn’t connect → permissions wrong or port 22 closed

• netstat missing → needed sudo apt install net-tools

• curl failing while ping worked → DNS or HTTP issue, not connectivity

• dig giving different results due to caching

• For some commands, tools simply weren’t installed

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📌 Commands That Helped Me Understand Stuff

These were the most useful this week:

# SSH login
ssh -i key.pem ubuntu@<ip>

# DNS record
dig +short example.com

# Port check
ss -tuln

# Check API or web server
curl -I http://<server-ip>

# Route packets take
traceroute google.com

They’re simple, but they exposed what was actually happening under the hood.

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📌 EC2 + Security Groups (My Biggest Learning)

Launch screen is easy.
The real learning:

• A perfectly healthy EC2 instance feels “dead” if SECURITY GROUPS rules block it

• SSH depends on two things: your key + SECURITY GROUPS

• HTTP/HTTPS need explicit opening

• Inbound/outbound rules matter more than I expected

• Understanding SECURITY GROUPS makes cloud debugging so much faster

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📌 What I Learned At The End

• Networking is not scary it is just logical once you break it down

• Small mistakes (like key permissions or blocked ports) cause the biggest headaches

• Understanding DNS and SECURITY GROUPS prevents most “why is this not working?” moments

• Tools like curl, dig, traceroute, and ss give real visibility

• Knowing fundamentals early makes everything else (Docker, Kubernetes, AWS networking) easier later

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📌 GitHub (All My Week 1 Tasks)

https://github.com/Harish1685/90DaysOfDevOps.git

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If you learned networking recently, I’d like to hear what confused you the most. Always open to suggestions.

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