These paths are called routes , and bridges keep internal tables that define how to get to a particular computer on the network. When some data arrives at the bridge, the bridge will look at the destination address of the data, and determine which network segment the data is to be transmitted on in order to get to its destination. Routers A bridge only uses the source and destination network card addresses, so does not know which department the computer belongs to. The bridge relies on physical information, but you really want to separate the computers using logical information. A router is a network component that divides the network logically based on logical numbers.
Switches Consider the following network.
This is because only one connection can exist at a time between a computer and a server. It is also a bit like a bridge in that it can be used to join networks together. BUT, a switch allows multiple connections between ports. This means that port1 can be connected to port2 at the same time as port 6 is connected to port7. As packets arrive at the switch, it looks at the MAC address in the header, and decides which segment to forward the packet to.