The following
sections describe both the star and extended-star topologies.
Star Topology
When installed, the star topology resembles spokes in a bicycle wheel. It is made up of a
central connection point that is a device, such as a hub, switch, or router, where all the
cabling segments actually meet. Each device on the network is connected to the central
device with its own cable.
Although a physical star topology costs more to implement than the physical bus topology,
the advantages of a physical star topology make it worth the additional cost. Each device is
connected to the central device with its own wire, so that if that cable has a problem, only
that one device is affected, and the rest of the network remains operational. This bene?¬?t is
important and is the reason why almost every newly designed Ethernet LAN has a physical
star topology. Figure 1-9 depicts a star topology with all transmissions going through a
single point.
Extended-Star Topology
A common deployment of an extended-star topology is in a hierarchical design such as a
WAN or an Enterprise or a Campus LAN. Figure 1-10 shows the topology of an extended
star.
16 Chapter 1: Building a Simple Network
Figure 1-9 Star Topology
Figure 1-10 Extended Star Topology
Exploring the Functions of Networking 17
The problem with the pure extended-star topology is that if the central node point fails,
large portions of the network can become isolated.
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