Network bridging describes the action of network equipment that allows two or more Layer 2 networks, or two or more Layer 2 network segments, to create an aggregate network. Bridging is distinct from routing, which allows the networks to communicate independently as separate networks. A network bridge is a network device that connects multiple network segments.
In the picture below, a Netrounds Test Agent is configured and running in bridge mode. Test Agents support both port and VLAN bridging. This particular setup is used for inline IPTV testing and allows all IPTV traffic to pass through the Test Agent, which measures quality on the same channels as the set-top box joins.