A network bridge is a computer networking device that creates a single aggregate network from multiple communication networks or network segments. This function is called network bridging.Bridging is distinct from routing.
Routing allows multiple networks to communicate independently and yet remain separate, whereas bridging connects two separate networks as if they were a single network (hence the name "bridging"). In the OSI model, bridging is performed in the first two layers, below the network layer (layer 3). If one or more segments of the bridged network are wireless, the device is known as a wireless bridge and the function as wireless bridging.
There are four types of network bridging technologies: simple bridging, multiport bridging, learning or transparent bridging, and source route bridging.
Figure 1: An illustration of a network bridge