The Need for Redundancy in Networks

Networks need redundant links to improve the availability of the network. Eventually, something in the network will fail. A router power supply might fail, or a cable might break, or a switch might lose power. And those WAN links, drawn as simple lines in most drawings in this book, are actually the most complicated physical parts of the network, with many individual parts that can fail as well.

Depending on the design of the network, the failure of a single component might mean an outage that affects at least some part of the user population. Network engineers refer to any one component that, if it fails, brings down that part of the network as a single point of failure. For instance, in Figure 6-1, the LANs ...

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