What is a Network Bridge Device?

Large computer networks are often divided into smaller segments to manage traffic and improve performance. To ensure smooth communication and efficient data flow between these segments, a network bridge is used.

A network bridge is a hardware device or software application that connects two or more separate network segments, allowing them to operate as a single, unified network.

In this guide, we have explained about bridges in networking, their purpose, and how they work. You will also learn the uses of network bridge devices, their configuration, and basic troubleshooting.

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What is a Bridge in a Computer Network?

A network bridge is a device that connects two or more Local Area Networks (LANs) or network segments to allow the devices on different segments to communicate.

Operating at the data link layer (Layer 2) of the OSI model, a bridge works by filtering and forwarding data packets between network segments based on MAC addresses.

Network bridge maintains a table of MAC addresses called, forwarding table to intelligently decide whether to pass a packet to another segment or drop it based on its MAC address. A forwarding table works similarly to a routing table in routers.

Network Bridge Diagram

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What is the Purpose of a Network Bridge?

Here are the key purposes of a network bridge in networking:

● Connects separate network segments to form a unified network.

● Filters and forwards data based on MAC addresses to reduce unnecessary traffic.

● Improves network performance by minimizing collisions and segmenting traffic.

● Enables communication between devices on different segments.

● Maintains isolation where needed, while still allowing controlled data exchange.

Types of Network Bridges

There are 4 types of network bridges:

1. Transparent Bridge

It is the most commonly used type of network bridge in modern networks. It operates at the data link layer (Layer 2) and forwards data based on MAC addresses. Devices on the network are unaware of its presence, as it silently filters and forwards traffic to reduce collisions and improve performance.

Transparent bridges are widely used in Ethernet-based LANs to segment traffic without requiring any configuration from connected devices.

2. Translational Bridge

A translational bridge is designed to connect networks that use different communication protocols. For example, it can link an Ethernet network with a Token Ring network by converting data formats and addressing schemes between the two.

This type of bridge is especially useful in legacy environments where different network technologies need to coexist and communicate effectively.

3. Wireless Bridge

A wireless bridge connects two or more network segments using wireless signals instead of physical cables. It’s commonly used to extend networks across buildings, large campuses, or outdoor areas where laying cables is impractical.

Wireless bridges help maintain connectivity between distant segments while preserving bandwidth and reducing infrastructure costs.

4. Remote Bridge

A remote bridge is used to connect networks that are geographically separated, typically over WAN links. It allows two LANs in different locations to function as part of a single network. Remote bridges are often employed in enterprise environments to maintain unified communication across branch offices or data centers.

2 Models of Network Bridging

Network bridging can be implemented using different models depending on the physical layout and communication needs of the network. The two primary models are local bridging and remote bridging.

Local Bridging

Local Bridging refers to the connection of multiple LAN segments within the same physical location using local cables. This model allows devices on different segments to communicate directly at the data link layer.

It's commonly used in office buildings or campuses where multiple departments or floors need to be interconnected without routing traffic through external networks.

Local bridging ensures fast and efficient communication and is typically implemented using transparent or multiport bridges.

Remote Bridging

Remote Bridging, on the other hand, is used to connect LANs that are geographically separated. This model involves linking bridges over a Wide Area Network (WAN), allowing distant networks to function as a single logical network.

Remote bridging is useful for organizations with branch offices or remote facilities that need to share resources and maintain unified communication.

It often requires additional configuration and may involve wireless or VPN technologies to maintain secure and reliable connections.

Network Bridge vs Switch vs Router

Advantages of a Network Bridge

A network bridge is a valuable tool for optimizing performance, reducing congestion, and connecting different network segments. The following are its advantages

1. Divides a large network into smaller segments, reducing congestion.

2. Isolates collision domains, improving network efficiency.

3. Optimizes bandwidth usage by separating traffic across segments.

4. Devices communicate without knowing a bridge is present.

5. Filters traffic based on MAC addresses, enhancing security.

Disadvantages of a Network Bridge

It has limitations in scalability, performance in large networks, and traffic management. They are further explained below

1. Not ideal for large networks; can become a bottleneck.

2. Can introduce latency in high-traffic environments.

3. Only filters based on MAC addresses, not IP addresses.

4. Poor configuration may cause loops and outages.

5. Managing a bridge can be challenging in large setups.

How to Set up a Network Bridge

Configuring a network bridge involves setting up a device to connect two separate sub-networks (sub-LANs). While the steps can differ depending on the system you are using, this guide will focus on setting up a bridge on a Linux machine. Windows users will follow similar procedures with slight variations in terminology.

1. Evaluate the Network Interfaces

First, open a terminal and use the commands ifconfig or ip link to display the available network interfaces on your system. These are the interfaces that will be part of the bridge.

2. Install Bridge Utilities (if necessary)

You may need to install bridge utilities. On Debian-based systems, you can do this with:

3. Modify the Network Configuration

Next, update your network configuration file. For Debian-based systems, you typically edit the /etc/network/interfaces file using a text editor such as nano or vim. Add the following configuration:

Make sure to replace eth0, eth1, and br0 with the correct interface names for your setup.

4. Restart the Networking Service

Once you’ve updated the configuration, restart the networking service to apply the changes. On Debian-based systems, use:

or

This should cover the basic steps to get your network bridge working.

Troubleshooting Common Issues of the Network Bridge

If your network bridge isn't functioning correctly, here are some troubleshooting steps to help resolve common issues:

1. Ensure that the bridge is properly connected to the router or switch on both sides. Test the Ethernet cables by replacing them with new ones to rule out any issues with the cables themselves.

2. Revisit the network configuration file and ensure there are no mistakes or typos. Double-check that the interfaces are correctly set up.

3. Make sure there are no duplicate IP addresses within the bridged segments. Duplicate IPs can create network conflicts and disrupt communication.

4. Restart Devices

5. Use a tool like Wireshark to observe the network traffic. This can help you identify any unusual behavior in the data packets or routing, indicating issues with the bridge.

Conclusion

In summary, a network bridge is a crucial element in modern networking, particularly for connecting and managing data flow across different network segments.

By segmenting traffic and reducing congestion, bridging networks allows organizations to maintain efficient, scalable networks that can handle increased demands without compromising performance.

From LAN bridges that help organize local networks to multiport bridges for complex infrastructures, bridges provide a powerful means of managing network traffic and optimizing communication across devices.