Networking, OSI Model, IP Addressing, Subnetting, DNS, ARP, Storage, Volume Mounting & NFS (Complete Guide)

Day 6 was a deep dive into Linux networking and Linux storage — two pillars that every DevOps/Cloud/DevSecOps engineer must master.
From OSI layers to subnetting, and from disk partitioning to NFS sharing, today’s learnings helped me understand how systems communicate and store data in real environments.

Let’s break it down 👇

🌍 1️⃣ Understanding Networking in Linux

🔌 Network Interface

A network interface is the point where a computer connects to a network — physical or virtual.
Examples:

eth0, ens3, wlan0

Used for routing, communication, and network troubleshooting.

🧱 2️⃣ OSI Model — The 7 Layers Explained Simply

The OSI model explains how data travels across a network.
I learned each layer one by one:

⚫ Layer 1 — Physical

Transmits raw bits through cables, signals, fiber.
Devices: NICs, cables, switches.

🟣 Layer 2 — Data Link

Node-to-node communication.
Handles error detection & correction.
Contains MAC addresses.

🔵 Layer 3 — Network Layer

Responsible for routing, choosing best path for data.
Contains IP addressing.

🟢 Layer 4 — Transport Layer

Handles sequencing, reassembly, and flow control.
Two major protocols:

TCP → Reliable, connection-oriented (mail, web apps)
UDP → Fast, connectionless (gaming, streaming)

🟡 Layer 5 — Session Layer

Manages sessions between applications.
Establishes → Maintains → Terminates.

🔶 Layer 6 — Presentation Layer

Formats data, encrypts and decrypts.
Ensures sender & receiver interpret data correctly.

🔴 Layer 7 — Application Layer

Closest to users.
Common protocols:

HTTP/HTTPS → Web
SMTP/POP3 → Email
FTP → File transfer
DNS → Domain resolution

💡 3️⃣ IP Addressing, Subnet Masks & Classes

🟩 IPv4 Format:

a.b.c.d → Each part = 8 bits (0–255)

📘 IP Classes

Class A → /8 → 1.0.0.0
Class B → /16 → 128.0.0.0
Class C → /24 → 192.0.0.0

🧮 4️⃣ CIDR Notation & Subnetting

Example: `192.168.1.0/24`

Network Address: 192.168.1.0
Broadcast Address: 192.168.1.255
Usable Hosts: 192.168.1.1 → 192.168.1.254

🔹 Subnetting /24 into 4 subnets

Each block size = 256 / 4 = 64

a) 192.168.1.0 → 192.168.1.63
b) 192.168.1.64 → 192.168.1.127
c) 192.168.1.128 → 192.168.1.191
d) 192.168.1.192 → 192.168.1.255

Subnetting helps design secure, efficient VPC networks.

🌐 5️⃣ DNS (Domain Name System)

DNS acts like the Internet’s phonebook:

👉 Converts domain names → IP addresses
Example:
www.google.com → 142.250.x.x

Makes the internet usable without remembering IP numbers.

🔗 6️⃣ ARP (Address Resolution Protocol)

ARP maps:
IP Address → MAC Address

Used inside local networks so devices find each other.
Critical for routing, switching, and troubleshooting LAN issues.

💾 7️⃣ Storage in Linux — RAM, Disk & 3 Storage Layers

🧠 RAM

Temporary storage (clears after reboot).

💽 HDD / SSD

Permanent storage for OS, logs, files, apps.

Linux storage works in 3 layers:

🟦 Layer 1 — Raw Disk Partitioning

Splitting a disk into sections.
Example: 10GB → 5GB + 5GB partitions.

🟩 Layer 2 — File System

Formatting partitions using:

ext4
xfs
btrfs

🟧 Layer 3 — Mount Points

Connecting the formatted partition to a usable folder.

🛠️ 8️⃣ Practical: Attaching a Volume to a VM & Mounting It

I practiced attaching a new volume to a Linux VM.

📌 Step 1 — Create VM

Launch instance, configure security groups.

📌 Step 2 — Create Volume

Choose size → select same availability zone as VM.

📌 Step 3 — Attach Volume

Inside VM, partition disk:

sudo fdisk /dev/nvme1n1

📌 Step 4 — Format the Partition

sudo mkfs.ext4 /dev/nvme1n1p1

📌 Step 5 — Mount the Disk

sudo mount /dev/nvme1n1p1 /mnt/data1

Now the new disk is active and usable.

📁 9️⃣ Practical: NFS (Network File System) Setup

I configured file sharing between two VMs:
nfs-server and nfs-client.

🖥️ Server Configuration

sudo mkdir -p /srv/nfs_server
sudo chown nobody:nogroup /srv/nfs_server
sudo chmod 777 /srv/nfs_server
sudo vi /etc/exports   # added export rule for client
sudo systemctl restart nfs-kernel-server

📌 Important:
Open port 2049 in the security group.

💻 Client Configuration

sudo mkdir -p /mnt/nfs_client
sudo mount <Server-IP>:/srv/nfs_server /mnt/nfs_client

Here the NFS server storage becomes accessible to the client VM.

🎯 Day 6 Takeaway

Today’s learning helped me build deeper understanding of:

✔️ OSI layers & network fundamentals
✔️ Classes, CIDR, subnetting & broadcast concepts
✔️ DNS & ARP — how computers find each other
✔️ Linux storage architecture
✔️ Disk partitioning, formatting & mounting
✔️ NFS server-client communication

These are foundational skills for cloud networking, DevOps automation, Kubernetes clusters, and secure infrastructure design.

Excited for Day 7! 🚀

Command Palette