A bridge is a device which filters data traffic at a specific network boundary. Bridge reduces the amount of traffic on a LAN by dividing it into two segments.Bridge performs at the data link layer i.e on layer 2 of the OSI model. Bridges investigate the incoming traffic and decide whether to forward it or discard it. For example, an Ethernet bridge inspects each incoming Ethernet frame, including the source and destination of MAC addresses. It sometimes help determine the frame size for making individual forwarding their decisions. This serves as a similar function as switches which also operate at Layer 2. Traditional bridges support one network boundary, whereas switches usually provide four or more hardware ports. Switches are sometimes called as multi port bridges for this reason. It is simply a device that connects two local area networks or LANs or two segments of the same LAN which use the same protocol such as Ethernet or Token Ring. A bridge is a piece of device which allows to merge a large network into two less significant and more competent networks. Moreover, a bridge can attach an older cabling scheme as well as a modern network on a single track. A bridge supervises the transfer of data on both the sides of the network, so that it can go by packets to the accurate location in a sequential manner. Most bridges listen to the network and mechanically shape out the address of each PC on either sides of the bridge. It can examine each communication and if required, it transmits it on the other side of the network. It manages the traffic to preserve optimum presentation on both the sides of the network.