A bridge router is a hardware device that both connects two local area computer networks (LANs) and directs the traffic within each. In other words, a bridge router, also called a brouter, combines the functions of both a bridge and a router into a single device. The bridge portion is a network Layer 2 switch, technology that was developed in the 1980s. Complex LANs, which are LANs with many subnets, also need a more recent device, a network Layer 3 switch called a router.
Two computer local area network segments or subnets use a bridge to connect them. All computers within a subnet must use the same protocol, e.g., Ethernet or Token Ring, although the individual segments may or may not use the same protocol. Breaking a LAN into subnets improves the speed within each. It is also necessary if some subnets use a different protocol from others.
Without a bridge, computers on one subnet cannot communicate with computers on another. A large LAN, such as one that covers an entire company, will likely need one or more bridges. A home network, which is usually quite small, is unlikely to need one at all.
A router acts like a network traffic cop: it tells information packets which network path to take to reach their destination. To do this, the router maintains tables of information. These enable the router to know which connections lead to particular groups of addresses. They also list what priority each connection has and what rules the router should use for handling both ordinary and special traffic.
Routers may be used to connect LANs to private wide area networks (WANs), and WANs to each other. The most common use is to connect LANs to the Internet. Using a bridge router where needed is less expensive than using both a bridge and a router, and provides equally good service.
Almost everyone who connects to the Internet has a router in his house or office. It is the device that connects computers to the cable, DSL, or optical fiber modem. It directs traffic from the local network to the Internet and back again.
A home network could have a bridge router rather than router or a wireless router. Most home LANs use a peer-to-peer network system to connect only a few computers, however, so a bridge is not needed. Most routers and bridge routers have a security system available that includes a firewall to help protect against unwanted intrusions from the Internet or from drive-by computer data thieves.
