Cisco Systems 3550 manual Module Slots” section on page 1-6 for Cisco-recommended

Chapter 3 Troubleshooting

Diagnosing Problems

Table 3-1 Common Problems and Solutions (continued)

Problem	Solution
No connectivity	• Verify that the devices at both ends of the link are connected
	and powered.
	• Verify that the autonegotiation settings are the same at both
	ends.
	• Verify that you are using the appropriate Ethernet cable for the
	connected device. See Table 2-1 on page 2-17for cabling
	requirements.
	• Verify that the cable is good by testing it on another device.
	Replace it with a known working cable.
	• STP might be checking for possible loops. Wait 30 seconds for
	the port LED to turn green.
	• For 1000BASE-T connections, make sure to use a twisted
	four-pair, Category 5 cable.
	• The switch is not recognizing a GBIC module. See the “GBIC
	Module Slots” section on page 1-6for Cisco-recommended
	GBIC modules, and see your GBIC module documentation for
	more information.
Poor performance or excessive	• There might be a speed and duplex autonegotiation mismatch.
errors	Use the show controllers ethernet-controller privileged
	EXEC command to display per-port send and receive statistics
	read from the hardware. You can also use the show interfaces
	privileged EXEC command to display the administrative and
	operational status of all ports or a specified port.
	• The cabling distance might be exceeded. Reduce the cable
	length to within the distances listed in the “Front-Panel
	Description” section on page 1-4.

Catalyst 3550 Switch Hardware Installation Guide

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