Using the tap device (bridging)
A special use case for a tap-based configuration is bridging. The term bridging applies to a feature of the operating system to bridge two network adapters together. When two (or more) adapters are bridged, all Ethernet traffic that is received on one of the adapters is forwarded out to all other adapters that are part of that bridge. This makes it possible to join (bridge) two network segments together and make it appear as if it is a single Ethernet broadcast domain. Common use cases for bridges are as follows:
The VPN clients need to be fully and transparently integrated into the server-side LAN. Note that the same effect can often be achieved using a
proxy-arpsetup.Some older computer games only allow multiuser games when all computers are part of the same broadcast domain.
Some legacy network protocols, notably the original Microsoft NetBIOS (non-TCP/IP-based) protocol, do not work well across network routers, or even assume a fully "flat" network space...
