Network Bridge is a device that connects two networks and it follows all the characteristics of Data Link Layer (Layer 2) of OSI Reference Model. The basic working principle of a network bridge lies in identifying & passing signal to another network by understanding the MAC addresses of each part. A MAC address, being unique all over the world, easily identifies the source & destination system in a bridged network. In the case of TCP/IP, bridge works with NetBEUI which is a non-routable protocol. Network Bridge is a must if a Wi-Fi & a wired network are to be connected. The Ad Hoc connection is necessary for internet sharing although some Wi-Fi cards may differ due to the manufacturing process.
A bridge has a foot in each network and acts on the link layer (level 2). It is able to pass frames from one network to another in an intelligent manner. A bridge, after a period of learning, is able to identify MAC addresses of nodes on each side of the bridge. It prioritizes the frames that actually need to be transferred, so that the traffic on each side is best. A bridge is very effective if the two networks A and B hardly communicate with each other; otherwise, it is best to communicate with an Ethernet cable for example.
A network bridge is independent of the higher network layers. In other words, a bridge will also function well with TCP / IP protocol with a non-routable (not logical address) as NetBEUI.
It is imperative that network protocols are the same on each side of the bridge, making the exchange at the level of frames. A bridge cannot interconnect two Ethernets, one using TCP / IP and the other another protocol (IPX / SPX, for example).
Two physical networks bridged appear as a single physical network. At the network layer (and upper), the bridge is transparent. This is a crucial detail.
The principle of the bridge is included in the "switches" that could be considered as advanced HUBS, creating bridges between the network cards exchanging data, using their MAC addresses
A bridge is a special gateway that is used within a single physical network to optimize traffic frames on the network. It can block the navigation if the network layer is poorly configured. To remove it, you must disable the 2PCs (or more) using it, or even repeating the network layer correctly.
XP network bridge: between a wired network and a Wi-Fi network
It may be that we want to share an internet connection with another PC connected on Wi-Fi Ad-Hoc, in addition to other PCs connected by a wired network. In this case it is necessary to create a network bridge between the two network interfaces (wired and Wi-Fi) of the PC sharing the same internet connection. However, some Wi-Fi cards cannot work this way. Indeed once the bridge created, the Wi-Fi is no longer operational.
To fix this small problem, you should:
In a DOS window, type the following command:
netsh bridge show adapter
Locate the card number responding when the bridge is active. If he says that your card is not in compatibility mode then do this:
netsh bridge set adapter x forcecompatmode=enable
Replace x by number of your card displayed following the previous command.