What is the purpose of a subnet mask, and how is it used in IP addressing?

🔹 What is a Subnet Mask & How is it Used in IP Addressing?

1️⃣ What is a Subnet Mask?

A subnet mask is a 32-bit number that helps divide an IP address into network and host portions. It determines which part of an IP address belongs to the network and which part identifies a specific device (host) within that network.

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2️⃣ How Does a Subnet Mask Work?

Each IP address consists of two parts:
✔ Network Portion (Identifies the network)
✔ Host Portion (Identifies devices within the network)

A subnet mask helps differentiate these two parts.

Example (IPv4 Addressing):

📌 IP Address: 192.168.1.10
📌 Subnet Mask: 255.255.255.0

🔹 Network Portion: 192.168.1 (determined by 255.255.255.0)
🔹 Host Portion: .10 (specific device in the network)

This means all devices with IPs 192.168.1.x belong to the same network.

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3️⃣ Common Subnet Masks & Their Uses

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4️⃣ Why is a Subnet Mask Important?

✅ 1. Efficient IP Address Allocation – Prevents waste of IP addresses.
✅ 2. Improves Network Performance – Reduces broadcast traffic.
✅ 3. Enhances Security – Isolates networks for better control.
✅ 4. Enables Subnetting – Allows creating multiple smaller networks from a larger one.

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5️⃣ Example: How Subnet Masks Help Identify Networks

Let’s compare two IP addresses:
🔹 192.168.1.5 and 192.168.2.8
🔹 Subnet Mask: 255.255.255.0

👉 The first three octets (192.168.1) define the network.
👉 Since 192.168.1.5 and 192.168.2.8 have different third octets, they belong to different networks.

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6️⃣ Summary

🔹 A subnet mask helps separate network & host portions of an IP address.
🔹 It determines which devices can communicate within a network.
🔹 Used to optimize IP address allocation & improve security.