Physical LAN topologies define how the end systems are physically interconnected. In shared media LANs, end devices can be interconnected using the following physical topologies:
In Star topology, all end devices are connected to the central device.Early star topologies interconnected end devices using Ethernet hubs. However, star topologies now use Ethernet switches. The star topology is easy to install, very scalable (easy to add and remove end devices), and easy to troubleshoot.
All the data on the star topology passes through the central device before reaching the intended destination. Hub/Switch acts as a junction to connect different nodes present in Star Network, and at the same time it manages and controls the whole of the network. Depending on which central device is used, “hub” and “Switch” can act as repeater or signal booster. Central device can also communicate with other hubs and switch of different network.
Extended Star Topology
In an extended star topology, additional Ethernet switches interconnect other star topologies.
Bus Topology is the simplest of network topologies. All end systems (computers as well as servers) are connected to each other and terminated in some form on each end. Infrastructure devices such as switches are not required to interconnect the end devices. Bus topologies using coax cables were used in legacy Ethernet networks because it was inexpensive and easy to set up.
In the ring topology, end systems are connected to a single circle of cable. Unlike the bus topology, the ring does not need to be terminated. The signals travel around the loop in one direction and pass through each computer, which acts as a repeater to boost the signal and send it to the next computer. Ring topologies were used in legacy Fiber Distributed Data Interface (FDDI) and Token Ring networks.
Figure 3.21 illustrate physical LAN topologies