Cisco Systems RJ-45-to-AUX Switch Troubleshooting Tools, Cable Problems, Cross−Over Cables, 312

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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