Cisco Catalyst 3550 Hardware Installation Manual page 54

Diagnosing Problems
Table 3-1
Problem
No connectivity
Poor performance or excessive
errors
Catalyst 3550 Switch Hardware Installation Guide
3-4
Common Problems and Solutions (continued)
Solution
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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 2-17
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
Module Slots" section on page 1-6
GBIC modules, and see your GBIC module documentation for
more information.
There might be a speed and duplex autonegotiation mismatch.
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
Description" section on page
Chapter 3 Troubleshooting
for cabling
"GBIC
for Cisco-recommended
"Front-Panel
1-4.
OL-6155-01