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Chapter 4 Troubleshooting

Diagnosing Problems

•Verify the status of all ports. See Table 1-8 on page 1-10for 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. Re-enable the port if necessary.

•Verify the cable type. See Connector and Cable Specifications, page B-1

A powered device connected to a PoE port does not receive power:

•Verify the status of all the ports. See Table 1-8for descriptions of the LEDs and their meanings.

•Use the show interfaces privileged EXEC command to see if the port is error-disabled, disabled, or shutdown. Re-enable the port if necessary.

•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, and wireless access points, or IEEE 802.3af-compliant devices.

SFP Module

Use only Cisco SFP modules. Each Cisco module has an internal serial EEPROM that is encoded with security information. This encoding verifies that the module meets the requirements for the switch.

•Inspect the 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 modules that the switch supports.)

•Use the show interfaces privileged EXEC command to see if the port or module is error-disabled, disabled, or shutdown. Re-enable the port if needed.

•Make sure that all fiber-optic connections are clean and securely connected.

Interface Settings

Verify that the interface is not disabled or powered off. If an interface is manually shut down on either side of the link, it does not come up until you re-enable the interface. Use the show interfaces privileged EXEC command to see if the interface is error-disabled, disabled, or shut down on either side of the connection. If needed, re-enable the interface.

Ping End Device

Ping from the directly connected switch first, and then work your way back port by port, interface by interface, trunk by trunk, until you find the source of the connectivity issue. Make sure that each switch can identify the end device MAC address in its Content-Addressable Memory (CAM) table.

Cisco CGS 2520 Hardware Installation Guide

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