When a network failure occurs, time is of the essence. When a production network goes down,
several things are affected. The most important of these is the bottom line—network failures
cost money.
A good example is a call-center network. The company relies on the network to be available
for its employees so that they can take phone orders, answer inquiries, or perform other
business transactions that generate income. A failure in this environment needs to be diagnosed
and repaired in a timely manner. The longer the network is down, the more money the
company loses.
To minimize monetary and productivity losses, network failures must be resolved quickly.
Troubleshooting is an integral part of getting this done. Intimate knowledge of a network also
facilitates rapid resolution. Armed with a few troubleshooting skills and intimate knowledge of
your network, you can solve most problems rather quickly, thus saving money.
Hold on a minute. What if you’re new on the job and you don’t yet have an intimate
knowledge of the network? You can probably get up to speed quickly enough, right?
Although that may have been the case in the past, getting up to speed becomes an overwhelming
challenge in today’s complex networks. These networks consist of many facets of
routing, dial-up, switching, video, WAN (ISDN, Frame Relay, ATM, and others), LAN, and
VLAN technologies.
Figure 33.1 gives you an idea of how these technologies intertwine. Notice that ATM, Frame
Relay, Token Ring, Ethernet, and FDDI all are present. Each technology has its own properties
and commands to allow for troubleshooting. Various protocols are used for each of these technologies.
In addition, different applications require specific network resources. (At least the
seven-layer OSI model, which you will review in Chapter 36, “Protocol Attributes,” is used to
maintain a common template when designing new technologies and protocols.) It would take
you a long time to master all of the technologies implemented in the network and to be able to
solve network problems based on your knowledge of the network alone. All of these factors
contribute to today’s complex network environments.
There must be an easier, more logical way to efficiently and successfully troubleshoot without
having to become intimately familiar with every network environment. Well, you’ll be
happy to know that there is an easier option—following a troubleshooting model, which is discussed
in detail in this chapter. By following a troubleshooting model, the need for intimate
knowledge of the network is reduced. A troubleshooting model should be adopted to help
resolve network malfunctions and reduce downtime.
Let’s move on to discuss Cisco’s model in detail.