🔌 Network Switch

1. Definition

A switch is a networking device that connects multiple devices (computers, printers, servers) within the same Local Area Network (LAN) and forwards data intelligently based on MAC addresses.

2. How It Works

• Operates at Layer 2 (Data Link) of the OSI model.
• Each port on the switch learns the MAC address of the device connected to it.
• When a packet arrives, the switch looks up the destination MAC in its MAC address table and forwards the packet only to the correct port.
• This makes communication faster and reduces unnecessary traffic compared to older hubs (which broadcast to all ports).

3. Types of Switches

• Unmanaged switch:
  • Plug‑and‑play, no configuration needed.
  • Common in small home/office setups.
• Managed switch:
  • Configurable (VLANs, QoS, monitoring).
  • Used in enterprise networks.
• Layer 3 switch:
  • Combines switching (Layer 2) with routing (Layer 3).
  • Can make IP‑based forwarding decisions like a router.

4. Key Functions

• MAC learning: Builds a table of MAC addresses and ports.
• Forwarding/filtering: Sends packets only to the correct destination port.
• Broadcast control: Limits unnecessary traffic.
• VLAN support (in managed switches): Segments a LAN into smaller logical networks.

5. Example in Action

• In an office:
  • 20 PCs, 2 printers, and a server are all connected to a switch.
  • The switch ensures that when PC1 sends data to the server, only the server’s port receives it — not all 20 PCs.

6. Switch vs Router vs Hub

✅ Summary: A switch is the “traffic manager” inside a LAN. It connects devices and forwards data only where it needs to go, using MAC addresses. Modern networks rely on switches for efficiency, scalability, and security.