This problem is addressed by Cisco with the use of Switched Port Analyzer (SPAN). SPAN allows the switch
to copy all the packets that are sent to nodes connected to the switch ports and direct them to another port. In
essence, the designated switch port becomes a mirror of the monitored port or ports.

Cable Problems

When a cable problem surfaces, it usually appears as an intermittent problem; however, it can cause an
immediate failure. Intermittent errors are hard to troubleshoot, and you must keep in mind that almost any
connectivity issue can be cable related. You’ll need to replace cables with a cable you know works in order to
see if the change resolves your connectivity issue.
Multimeters, time domain reflectometers (TDRs), cable analyzers, and breakout boxes can be used to test for
cable problems, but they may not always find the trouble. Just because cables were installed by a certified
cable installer doesn’t mean that they aren’t improperly made, won’t break, or don’t have connector failures.
Cables are moving parts, and any moving parts are subject to wear and tear as well as failures.

Cross−Over Cables

When I am teaching classes, hardened Microsoft Certified Systems Engineers (MCSEs)s frequently have to
ask me what a rollover or crossover cable is. This doesn’t apply to all MCSE’s of course, since I am one
myself. I have always been on the networking side of technical support, so it is hard for me to believe that
long−time network administrators don’t know the differences between a straight−through and a cross−over
cable or when to use them.
A connection to a network node from a switch or hub uses a straight−through cable. A crossover cable is used
to connect two network devices: a hub to a hub, a switch to a switch, a switch to a router, and so on. Many
times in my classroom or on the job, I have come across someone who couldn’t get a connection between
switches because they were using a straight−through cable and should have been using a crossover cable. See
Chapter 2 for more information on cables and pinouts.
Switch Troubleshooting Tools
Catalyst switches provide quite a few diagnostic and administrative tools to assist administrators. These tools
are located in the IOS command−line interface located on each Cisco device and in the CiscoWorks for
Switched Internetworks (CWSI) external software for the end workstation.
Let’s take a look at some of the components of CWSI. Then we’ll examine the troubleshooting commands
you can use on the Cisco IOS that are found on Cisco’s line of enterprise switches.

CiscoWorks for Switched Internetworks

CWSI (also called Campus Manager) can run as a standalone application on Windows NT or Unix, including
Solaris, HP−Unix, and AIX. This application includes a number of components that not only aid in
troubleshooting but also help you during installation and monitoring. These components are as follows:
CiscoView—A graphical user interface (GUI) application that provides a virtual look at the switch’s
chassis, configuration, and performance monitoring. This component provides very little in the way of
troubleshooting functionality. A screen capture of CiscoView is shown in Figure 16.3.
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