Glossary
What is a network bridge? | ExpressVPN Glossary

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Network bridge

What is a network bridge?

A network bridge is a piece of hardware, software, or firmware that links two or more physically separated network segments. It allows devices on those segments to communicate with each other as part of the same network.

How a network bridge works

The role of bridges in networks. Network bridges connect network segments that may be separated by distance, physical barriers, or different types of transmission media (like Ethernet and Wi-Fi). They can help extend or join local area network (LAN) segments.

They can take the form of a physical device, often built into equipment such as a wireless access point (WAP), or a software component. Operating on the data link layer (Layer 2), a network bridge forwards traffic between endpoints using Media Access Control (MAC) addresses. Endpoints can refer to devices such as computers, phones, and other networked devices.

As the bridge receives traffic, it records the source MAC addresses and the associated ports within a table. If it doesn’t yet know which port a destination MAC address is on, it forwards the frame to other ports; once it has learned the destination’s port, it forwards frames only to that port.

Types of network bridges

Network bridges come in several forms, varying in terms of primary use and other factors. These include:

Transparent bridge: A bridge that is effectively invisible to other devices on the network. These can filter and forward traffic without requiring changes to end devices.
Wireless bridge: Any network bridge that connects network segments via a wireless connection medium. They're commonly used to extend local networks between areas where running cables is impractical (for example, in large buildings or outdoor spaces).
Multiport bridge: Bridges that combine more than two network segments into a single broadcast domain. In some contexts, the term "network switch" is used interchangeably with multiport bridge.
Translational bridge: Operates between network segments using different transmission media. It translates frames between media so traffic can pass between segments.

Network bridge vs. network switch

A network switch is essentially an evolution of a network bridge. Compared to traditional two-port bridges, switches are designed to handle more ports more efficiently. Both work mainly on the data link layer and learn MAC addresses to forward and filter traffic across multiple network segments.

The main differences usually concern scale and performance. Switches are generally built for larger networks with more connected devices and higher traffic. To accommodate the increased traffic more efficiently, they also tend to have more advanced routing and optimization capabilities.

	Network bridge	Network switch
Primary role	Connects two parts of a local network	Connects many devices within a local network
Open Systems Interconnection (OSI) layer	Layer 2 (data link layer)	Primarily Layer 2 (some also support Layer 3)
Performance	Limited, not optimized for high traffic	High-performance, hardware-accelerated
Typical form	Software or simple hardware	Typically dedicated hardware
Common features	Basic MAC forwarding	Virtual local area networks (VLANs), Spanning Tree Protocol (STP), and Quality of Service (QoS)

Limitations of bridges

Drawbacks of network bridges include:

Slower performance than switches: Added latency can occur, especially in software-based bridges or when traffic can't be offloaded efficiently.
Not ideal for large or complex networks: Network bridges can become harder to manage and more prone to congestion or wide-impact faults.
Limited traffic control: Because a bridge operates only at Layer 2, it primarily forwards and filters traffic based on frame/MAC information rather than IP routing.
Misconfiguration risk: Loops and outages can occur if a network bridge is not set up properly.

Common use cases

The role of a bridge is to couple different parts of a local area network and forward traffic between them. Some of the reasons or applications for network bridges are:

Translating between transmission media, such as wired and wireless segments.
Expanding LANs without replacing infrastructure.
Extending home networks for gaming or streaming devices.
Connecting virtual machines with physical networks.
Linking separate LAN segments, even when each segment uses switches.
Integrating legacy infrastructure with newer networks.
Configuring a PC as a bridge to connect network segments.

FAQ

Is a bridge the same as a router?

No, a bridge connects network segments across a single local area network (LAN). A router connects different networks (or subnets), such as a LAN to a wide area network (WAN) or the internet. Bridges generally operate on Layer 2 (the data link layer), while routers operate on Layer 3 (the network layer).

Can a PC act as a network bridge?

Yes, operating systems such as Windows and Linux, and certain virtual machine (VM) platforms, often include bridging capabilities. There are also specialized software programs for network bridging.

Is a bridge still used today?

Yes, bridging is still widely used, often in the form of network switches and virtual bridges that connect local area network (LAN) segments at Layer 2. Bridges are also commonly used in simpler or smaller networks, and in specific setups (such as virtualization) where network segments need to be joined.

Does a bridge improve Wi-Fi?

Bridges don’t directly increase Wi-Fi speed, but they can help extend a network to new areas, for example, by linking segments over a dedicated bridge. Compared with Wi-Fi repeating/mesh setups, bridging can avoid some performance loss caused by over-the-air retransmission. In some designs, bridging can also limit unnecessary traffic between network segments by forwarding data only where it needs to go.

What layer does a bridge operate on?

A network bridge operates on the data link layer, also known as Layer 2 of the Open Systems Interconnection (OSI) model. This layer is responsible for transferring data between network nodes and for detecting transmission errors.