Bridges

Bridges are used to interconnect LANs using one or more of the IEEE 802.x standards, that is Ethernet or Token Ring LAN environments and also others. Bridges are devices with two or more ports, which connect LANs at the Data Link layer of the OSI Model. The purpose of bridges is to allow nodes connected to different LANs to communicate as if they were located on the same LAN. In contrast to repeaters, that use …

…routes, and will not have to re-transmit every time a packet is sent if the bridge knows that the destination node address is connected to the same port as the bridge saw the packet on. Forwarding table entries also age, so if a given address has not been heard from in a specified period of time then the address is deleted from the forwarding table. The bridging method for Ethernet networks is called Transparent Bridging.