Introduction

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If you’ve ever worked with networks, you’ve probably heard the terms Subnet and VLAN. They both help organize a network and keep things running smoothly—but they’re not the same! → Subnets work at the Network Layer (Layer 3) and use IP addresses to divide a big network into smaller sections. → VLANs (Virtual Local Area Networks) work at the Data Link Layer (Layer 2) and group devices logically within a switch, even if they’re not physically close.

Both help control network traffic, improve security, and make management easier. But how do they actually work? And when should you use one over the other?

Let’s break it down step by step!

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What is a Subnet?

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A Subnet (short for subnetwork) divides a big network into smaller chunks → makes traffic flow better → improves security.

Key Features of Subnets

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→ Layer 3 (Network Layer) – Uses IP addresses. → Divides IP Networks – Each subnet has its own range. → Router is Needed! – Devices in different subnets must use a router to talk. → Limits Broadcast Traffic – Stops unnecessary network noise.

Example

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Imagine an office with 200 devices. Instead of one big messy network:

• 192.168.1.0/24 → Management PCs

• 192.168.2.0/24 → Employees’ Computers

• 192.168.3.0/24 → Guest Wi-Fi

Each subnet = a separate IP range – needs a router to talk to other subnets.

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What is a VLAN?

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A VLAN (Virtual Local Area Network) segments a network virtually → without needing separate physical networks.

Key Features of VLANs

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→ Layer 2 (Data Link Layer) – Uses MAC addresses. → Virtual Segmentation – Group devices logically, even if they’re on different switches. → Uses VLAN IDs – Each VLAN has a unique identifier (e.g., VLAN 10, VLAN 20). → Requires a Managed Switch – VLAN support is a must! → Limits Broadcasts – Just like subnets, but at Layer 2. → Needs a Router (or Layer 3 Switch) for Inter-VLAN Traffic

Example

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Same office setup, but with VLANs:

• VLAN 10 → Management PCs

• VLAN 20 → Employees’ Computers

• VLAN 30 → Guest Wi-Fi

All on the same switch but logically separated → router or Layer 3 switch needed for communication.

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Subnet vs VLAN: The Differences

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Feature	Subnet	VLAN
Layer	Layer 3 (Network)	Layer 2 (Data Link)
Defined By	IP Addressing	VLAN ID
Separation Method	Routers	Switches
Traffic Isolation	Needs separate IP networks	Can be done within the same switch
Broadcast Control	Reduces broadcasts by IP subnetting	Limits broadcasts within VLANs
Flexibility	Fixed to IP address ranges	Can group devices logically, regardless of location

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When to Use Subnets vs VLANs?

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Use Subnets When:

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→ You need to separate networks using IP addressing. → You want to restrict access between devices (e.g., guests vs employees). → You have devices in different physical locations that need routing.

Use VLANs When:

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→ You need logical separation without changing IP addressing. → You want to group devices based on function (e.g., VoIP phones, workstations). → You need to control broadcast domains inside a switch.

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Can You Use Both Together?

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YES! → In most networks, subnets and VLANs work together.

A common setup:

• VLAN 10 → 192.168.1.0/24 (Management)

• VLAN 20 → 192.168.2.0/24 (Employees)

• VLAN 30 → 192.168.3.0/24 (Guest Wi-Fi)

VLANs = Logical grouping inside a switch. Subnets = IP-based segmentation for communication.

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Conclusion

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Subnet vs VLAN → They both segment a network, but how they do it is different!

• Subnets = Layer 3 (IP-based), uses routers.
• VLANs = Layer 2 (MAC-based), uses switches.

In most cases – use both! → VLANs for logical grouping + Subnets for IP organization.