Cisco Systems RJ-45-to-AUX manual Switch Troubleshooting, Hardware Troubleshooting, No Power, 309

Chapter 16: Switch Troubleshooting

In Depth

Switch troubleshooting includes both hardware and software. The switch hardware can be anything from a Supervisor Engine to a module, card, chassis, or even a power supply. The software can be the individual module software or the IOS.

In this chapter, we will focus on troubleshooting both the Command Line Interface (CLI) and the Set/Clear command−based IOS. First, I will concentrate on the physical hardware and then on the IOS troubleshooting commands. I will focus not only on the switch configuration but also on troubleshooting virtual LANs (VLANs) and the Spanning−Tree Protocol (STP).

Hardware Troubleshooting

The most common hardware problems are power supply problems, failed modules or interface problems, failed RAM, and cabling issues. Let’s first take a look at what to do in the event of a power failure, the boot−up POST, and the different indicator lights that can be used for troubleshooting.

Warning	The following steps are my recommendation, based on troubleshooting procedures I use
	every day. These steps do not come from Cisco documentation.

No Power

The first indicator of a problem is the failure of a switch to power up. If there is no power to the switch, meaning the fan does not power up and no indicator lights appear lit on the front or back of the switch, follow these steps:

1.Check the physical cable for breaks or an unsecure connection.

2.Check the outlet with a multimeter for proper throughput.

3.Reseat the RAM in the chassis.

4.Check the connection and verify that all interfaces, cards, and modules are securely fastened in the chassis.

Warning	Make sure you use proper grounding techniques before removing or touching any
	components, and that the switch is unplugged from all power sources.

5.Make sure all gold−plated connections for the cards, modules, and RAM are not corroded and can make a good connection. To clean the gold−plated connections, I use an eraser from a pencil.

6.If necessary, contact Cisco Technical Assistance Center (TAC) or an authorized Cisco repair vendor for further troubleshooting steps and replacement parts.

Tip Heat from a failed fan followed by a cooling of components in the switch can cause a flexing of the connections. By reseating the connections, you can resolve the problem.

POST

The power on self test (POST) can be a powerful tool in solving hardware issues. On the 1900 and 2820 series switches, the POST is not displayed on the screen. Instead, as the switch powers up, all the LEDs are lit except the LED that represents the test the switch is performing. The LEDs and their related tests are shown in Table 16.1.

Table 16.1: The LEDs and the POST tests they represent.

309