What is Bridge? – Network Devices

A bridge is a network device used to connect two or more network segments, allowing them to function as a single network. It operates at the Data Link Layer (Layer 2) of the OSI model, using MAC addresses to filter and forward data to its intended destination. By dividing networks into segments, a bridge improves network efficiency and reduces traffic congestion.

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Key Characteristics of a Bridge

1. Operates at Layer 2
   • A bridge works at the Data Link Layer (Layer 2) of the OSI model, handling data based on MAC addresses.
2. Collision Domain Segmentation
   • It divides a network into multiple segments, isolating collision domains to improve performance.
3. Traffic Filtering
   • A bridge examines the destination MAC address of incoming frames and forwards them only to the appropriate segment.
4. Protocol Independence
   • It connects network segments using the same Layer 2 protocol, such as Ethernet.
5. Broadcast Handling
   • A bridge forwards broadcast traffic to all connected segments unless it is explicitly filtered.

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Main Functions of a Bridge

1. Connecting Network Segments
   • A bridge connects two or more LAN segments, making them operate as one.
2. Traffic Management
   • It filters and forwards data based on MAC addresses, reducing unnecessary traffic in the network.
3. Enhancing Performance
   • By isolating collision domains, it decreases traffic collisions and improves overall network efficiency.
4. Broadcast Traffic Regulation
   • A bridge helps control broadcast traffic, preventing network congestion caused by excessive broadcasting.

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Types of Bridges

1. Local Bridge
   • Connects segments within the same physical network.
2. Remote Bridge
   • Connects network segments located in different physical locations, typically over WAN connections.
3. Wireless Bridge
   • Connects network segments wirelessly, often used to extend a network to areas where cabling is impractical.

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Advantages of a Bridge

1. Network Segmentation
   • Divides a network into smaller collision domains, improving efficiency.
2. Reduced Traffic
   • Prevents unnecessary traffic by forwarding data only to the intended segment.
3. Cost-Effective
   • Provides an economical solution to extend or manage networks compared to routers.
4. Scalability
   • Allows networks to expand by connecting additional segments.

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Disadvantages of a Bridge

1. Limited Speed
   • The connected segments must operate at the same speed, which can be a bottleneck in high-speed networks.
2. Inferior to Switches
   • Bridges are less powerful and versatile compared to modern switches.
3. Complex Management
   • Managing multiple bridges in a large network can be challenging.
4. Broadcast Storms
   • Excessive use of bridges can lead to broadcast storms, which can overwhelm the network.

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Bridge vs. Other Network Devices

Feature	Bridge	Switch	Router
OSI Layer	Layer 2 (Data Link Layer)	Layer 2 (and sometimes Layer 3)	Layer 3 (Network Layer)
Data Handling	Based on MAC address	Based on MAC and sometimes IP address	Based on IP address
Collision Domain	Separates collision domains	Each port has its own collision domain	Each network has its own collision domain
Broadcast Domain	All segments share the same domain	All ports are in the same domain	Each network is in a separate domain
Performance	Moderate	High	High

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Use Cases for Bridges

1. Small Network Extensions
   • Useful in small LAN environments to connect segments and manage traffic.
2. Wireless Connectivity
   • Wireless bridges can extend network connectivity to remote locations.
3. Traffic Management
   • Bridges help reduce unnecessary traffic and improve overall network performance.
4. Network Integration
   • Connects two or more networks using the same protocol, enabling seamless integration.

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Modern Relevance of Bridges

• In today’s networks, switches have largely replaced bridges due to their advanced capabilities, such as higher performance, VLAN support, and more efficient traffic management.
• Wireless bridges are still commonly used to extend networks wirelessly.
• Despite their simplicity, bridges remain useful in specific scenarios like legacy network environments or small-scale networks.

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A bridge is an essential tool for connecting and segmenting networks efficiently.