Network Interconnection Devices: Repeaters, Hubs, Bridges, Switches, Routers, and Gateways
To link separate cables, local networks, and different protocols together, engineers use specialized connecting hardware devices.
Each device operates at a specific layer of the ISO OSI Reference Model.
1. Summary of Devices Across the OSI Layers
Layer 7: Application Layer ───▶ GATEWAY (Protocol Converter)
Layer 6: Presentation Layer ──▶ GATEWAY
Layer 5: Session Layer ───────▶ GATEWAY
Layer 4: Transport Layer ─────▶ GATEWAY
Layer 3: Network Layer ───────▶ ROUTER / Layer-3 Switch (IP Addresses)
Layer 2: Data Link Layer ─────▶ BRIDGE / SWITCH (MAC Addresses)
Layer 1: Physical Layer ──────▶ REPEATER / HUB (Raw Electrical Bits)2. In-Depth Breakdown of Each Device
Network Interconnection Devices
1. Repeater (Layer 1)
Regenerates and boosts weak electrical/optical signals
2. Hub (Layer 1)
Multi-port repeater; blindly broadcasts signals out of all ports
3. Bridge (Layer 2)
Filters traffic between 2 LAN segments using MAC address tables
4. Switch (Layer 2)
Multi-port bridge; forwards frames directly to destination port
5. Router (Layer 3)
Connects different networks; routes packets using logical IP addresses
6. Gateway (Layer 7)
Translates completely different protocol suites (e.g., AppleTalk to TCP/IP)
Key Comparisons:
- Hub vs. Switch: A Hub is “dumb”—data entering port 1 is shouted out of all ports (huge collision domain). A Switch is “intelligent”—it maintains a MAC table and sends data only to the specific port where the destination computer is connected (each port is an isolated collision domain).
- Switch vs. Router: A Switch works with MAC addresses inside the same local network. A Router works with IP addresses to move packets between completely different networks (e.g., your college LAN and the Internet).
3. Master Comparison Table for University Exams
| Device Name | OSI Operating Layer | Primary Addressing Used | Intelligence Level | Collision Domains | Broadcast Domains |
|---|---|---|---|---|---|
| Repeater | Layer 1 (Physical) | None (Electrical Bits) | Non-intelligent | 1 single domain | 1 single domain |
| Hub | Layer 1 (Physical) | None (Electrical Bits) | Non-intelligent | 1 single domain | 1 single domain |
| Bridge | Layer 2 (Data Link) | 48-bit MAC Address | Software-filtered | Splits into 2 domains | 1 single domain |
| Switch | Layer 2 (Data Link) | 48-bit MAC Address | Hardware ASIC-filtered | 1 per port (Isolated) | 1 single domain |
| Router | Layer 3 (Network) | 32-bit/128-bit IP Address | Intelligent Software/ASIC | 1 per interface port | Splits broadcast domains! |
| Gateway | Layers 4 to 7 (All) | Full Protocol Stacks | Highly intelligent | Separated networks | Separated networks |
💡 DAVV Exam Tip
Guaranteed Exam Question (10 Marks): “Explain various network interconnection devices. Differentiate between Hub, Switch, Router, and Gateway.”
- Write down the OSI layer mapping for every single device.
- Include the 6-parameter master comparison table above.
- Mention: “A router breaks broadcast domains, whereas a switch breaks collision domains.” Examiners highlight this exact sentence!