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6-3
Catalyst 3850 Switch Hardware Installation Guide
OL-26779-02
Chapter 6 Troubleshooting
Diagnosing Problems
10/100/1000 Port Connections
A port appears to malfunction:
• Verify the status of all ports. See Table 1-5 on page 1-11 for descriptions of the LEDs and their
meanings.
• Use the show interfaces privileged EXEC command to see if the port is error-disabled, disabled, or
shut down. Reenable the port if necessary.
• Verify the cable type. See Appendix B, “Connector and Cable Specifications.”
PoE and PoE+ Port Connections
A powered device connected to a PoE port does not receive power:
• Verify the status of all ports. See Table 1-6 and Table 1-10 for descriptions of the LEDs and their
meanings.
• Use the show interfaces privileged EXEC command to see if the port is error-disabled, or disabled,
or shut down. Reenable the port if necessary.
• Verify that the power supply installed in the switch meets the power requirements of your connected
devices. See the “Power Supply Modules” section on page 1-18 for more information.
• Verify the cable type. Many legacy powered devices, including older Cisco IP phones and access
points that do not fully support IEEE 802.3af might not support PoE when connected to the switch
by a crossover cable. Replace the crossover cable with a straight-through cable.
Caution Noncompliant cabling or powered devices can cause a PoE port fault. Use only compliant cabling to
connect Cisco prestandard IP phones, wireless access points, or IEEE 802.3af-compliant devices.
Note The output of the PoE circuit has been evaluated as a limited power source (LPS) per IEC 60950.
SFP Modules
Use only Cisco network modules and SFP modules.
• Inspect the network module and SFP module. Exchange the suspect module with a known good
module.
• Verify that the module is supported on this platform. (The switch release notes on Cisco.com list the
SFP and SFP+ modules that the switch supports.)
• Use the show interfaces privileged EXEC command to see if the port or module is error-disabled,
disabled, or shut down. Reenable the port if needed.
• Make sure that all fiber connections are clean and securely connected.
• For CX1 module connections and fiber connections, make sure that cable routing does not violate
the minimum allowed cable bend radius. See the module documentation for specific cabling
requirements.