Connects different network segments at the Data Link layer. http://en.wikipedia.org/wiki/Network_bridges

A bridge routes on Layer 2 (MAC) addresses.

Its been a while since I've put one together hope this helps. Network Bridge Network Bridge removes the need for routing and bridging hardware in a home or small office network that consists of multiple LAN segments. With Network Bridge, multiple LAN segments become a single IP subnet, even if the LAN segments are of mixed network media types. Network Bridge automates the configuration and management of the address allocation, routing, and name resolution that is typically required in a network that consists of multiple LAN segments. for more info: https://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/security/

Wikipedia said it better than I ever could: A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model . Bridges are similar to repeaters or network hubs, devices that connect network segments at the physical layer, however a bridge works by using bridging where traffic from one network is managed rather than simply rebroadcast to adjacent network segments. In Ethernet networks, the term "bridge" formally means a device that behaves according to the IEEE 802.1D standard - this is most often referred to as a network switch in marketing literature. Since bridging takes place at the data link layer of the OSI model, a bridge processes the information from each frame of data it receives. In an Ethernet frame, this provides the MAC address of the frame's source and destination. Bridges use two methods to resolve the network segment that a MAC address belongs to. * Transparent Bridging – This method uses a forwarding database to send frames across network segments. The forwarding database is initially empty and entries in the database are built as the bridge receives frames. If an address entry is not found in the forwarding database, the frame is rebroadcast to all ports of the bridge, forwarding the frame to all segments except the source address. By means of these broadcast frames, the destination network will respond and a route will be created. Along with recording the network segment to which a particular frame is to be sent, bridges may also record a bandwidth metric to avoid looping when multiple paths are available. * Source route bridging – With source route bridging two frame types are used in order to find the route to the destination network segment. Single-Route (SR) frames comprise most of the network traffic and have set destinations, while All-Route(AR) frames are used to find routes. Bridges send AR frames by broadcasting on all network branches; each step of the followed route is registered by the bridge performing it. Each frame has a maximum hop count, which is determined to be greater than the diameter of the network graph, and is decremented by each bridge. Frames are dropped when this hop count reaches zero, to avoid indefinite looping of AR frames. The first AR frame which reaches its destination is considered to have followed the best route, and the route can be used for subsequent SR frames; the other AR frames are discarded. This method of locating a destination network can allow for indirect load balancing among multiple bridges connecting two networks. The more a bridge is loaded, the less likely it is to take part in the route finding process for a new destination as it will be slow to forward packets. A new AR packet will find a different route over a less busy path if one exists. This method is very different from transparent bridge usage, where redundant bridges will be inactivated; however, more overhead is introduced to find routes, and space is wasted to store them in frames. A switch with a faster backplane can be just as good for performance, if not for fault tolerance.

Bridge is a layer 2 device, used in a LAN environment to form collision domains.It extends the broadcast domain.

It filters,forwards or floods the layer two PDUs called 'frames'

Your computer connects to the internet through a modem, and each computer on your network can connect directly to that modem, or if this is not possible by limitations on the modems ports, they can be connected trough your computer, which relays messages to and from the internet for them. The comutrs on your network can also connect directly to each other to share files and printers. The network bridge basically connects parts of these networks together. So if you had three computers, one is the gateway which the other two connect to, and the gateway connects all three to the internet, but, heres where the bridge comes in, the two computers connected to it can not communicte with each other, since they are not directly connected. So you could run a wire between them, or set up a wireless network, but the easiest way is to use the already existing connections to your gateway computer. By using software to interface the devices connecting them to the gateway. Messages sent from a computer on the ntwork go to the ateway, it then resends them to the other network computer rather than the internet. The connection is on a very low level, as shown in other answers, which is all incomprehensible to me. A simplified explanation. Computer 1 connects to internet. Computer 2 connects to computer 1 Computer 3 connects to computer 1 Comuter 1 relays internet for all Bridge on computer 1 will connect 2&3 to each other. That's my guess at it, the explanations I've seen require a degree in computer lingo, so I' not really sure.

Quick answer, a bridge connects two different protocols (DSL to IP LAN, Broadband to IP LAN, etc). This is different than a router in that a router moves traffic within the same protocol (IP to IP) between two networks. Bridges are really pretty stupid, Routers are more intelligent, and can do much more. There are hybrids called Brouters, but most of that functionallity has been moved into routers.

Briefly, a bridge connects "similar" lan segments. A router connects "dis-similar" segments. A LAN segment is that piece of the wiring that has a unique identification, usually a different IP address, different IPX number (for a Novell network), or protocol type. (Ethernet vs. Token Ring). A bridge might be used to connect two different departments or buildings for a company. The network administrators may want to keep geographic areas seperate for the sake of troubleshooting, etc., but have them access the same applications, printers, etc., and, as such, would keep these areas on independant segments, bridged together. A bridge would allow these segments to see each other and use the same network resources. Usually, this bridge function is accomplished in the server by having two (or more) NICs (Network cards) in the server. You connection from your home computer to Ameritech (or whomever) to the internet will use a router because the Ameritech segment is dissimilar from your home segment. Hubs and switches are used within a segment to connect the various pieces of the segment. Hope that helps.

A bridge, as its name suggests, connects subnets within a LAN. "Bridges," incidentally have been supplanted by switches since the latter accomplish the same thing but in a better way. Switches devote the entire available bandwidth to the connection and, additionally, minimize network traffic.