Topologies

The topology of a network defines how the nodes of the network communicate with one another over the physical media. A LAN generally consists of one of three different topologies. 

BUS 

A bus topology is a straight line transmission media (the bus) which is terminated at both ends. Network nodes attach directly to the bus. This topology tends to be difficult to troubleshoot, since it is hard to isolate where a problem is occurring. Another drawback is a single break in the network will disable the entire network. A terminator is required at both ends of the bus to prevent the signal from bouncing back and forth along the cable. 

RING 

A ring is a bus which is in the shape of a ring - no ending and no beginning. Each node on the bus has a repeater which duplicates the signal and minimizes signal degradation. The ring topology has many of the same problems as the bus topology, in that it can be difficult to troubleshoot and a single break can disable the whole network. 

STAR 

A star topology consists of a point-to-point connection to a central connection, generally a hub or a switch. A hub will have two or more connectors, which allow two or more network nodes to be connected to the network. In more complex networks, you may have multiple hubs connected to a switch in a star configuration, with multiple nodes connected to each hub in additional star configurations.