What is the role of a network bridge?

A network bridge plays a crucial role in connecting and combining separate networks into one coherent unit. This is particularly important in scenarios where multiple segments of a network need to communicate but are physically separated, either due to distance or different network types.

Bridges operate at the data link layer (Layer 2) of the OSI model and are responsible for filtering traffic and ensuring that data packets are sent only to the appropriate devices within the combined network. This helps in reducing traffic and improving overall network efficiency. By facilitating communication between different network segments, bridges enhance the performance and scalability of network designs.

The other options do not accurately reflect the primary function of a network bridge. While managing data channels (first option) or optimizing routing paths (fourth option) are important tasks in networking, they are typically handled by different devices such as switches and routers. Moreover, defining the structure of network protocols (second option) pertains more to network standards and protocol layers rather than the operational function of a bridge.