Cisco Systems 3120 manual SFP Module Port Issues, Port and Interface Settings, Ping the End Device

Chapter 3 Troubleshooting

Diagnosing Problems

•Verify that you are using the correct cable type. See Appendix B, “Connector and Cable Specifications,” for more information.

•Test for loose connections. Sometimes a cable appears to be seated, but is not. Disconnect and then reconnect the cable.

SFP Module Port Issues

Use only Cisco small form-factor pluggable (SFP) modules on the switch module. Each Cisco module has an internal serial EEPROM that is encoded with security information. This encoding provides a way for Cisco to identify and validate that the module meets the requirements for the switch module. Test these items:

•Bad or wrong SFP module. Exchange the suspect module with a known, good module. Verify that this module supports this platform. See the “Cisco TwinGig Converter Module” section on page 1-4for a list of supported SFP modules.

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

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

Port and Interface Settings

Verify that the port or interface is not disabled or for some reason powered down. If a port or interface is manually shut down on one or the other side of the link, the link does not come up until you re-enable the port. Use the show interfaces privileged EXEC command to determine the port or interface error-disabled, disabled, or shutdown status on both sides of the connection. If necessary, re-enable the port or the interface.

Ping the End Device

Test the end device by pinging it from the directly connected switch module 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 module can identify the end device MAC address in its Content-Addressable Memory (CAM) table.

Spanning Tree Loops

Spanning Tree Protocol (STP) loops can cause serious performance issues that might appear to be port or interface problems. In this situation, the switch module bandwidth is used repeatedly by the same frames, crowding out legitimate traffic.

A unidirectional link can cause loops. This occurs when the traffic that the switch module sends is received by its neighbor, but the switch module does not receive the traffic that is sent from the neighbor. A broken fiber-optic cable, other cabling, or a port issue could cause this one-way communication.

You can enable the UniDirectional Link Detection (UDLD) protocol on the switch module to help identify difficult-to-find unidirectional link problems. UDLD supports a normal mode of operation (the default) and an aggressive mode. In normal mode, UDLD detects unidirectional links because of incorrectly connected interfaces on fiber-optic connections. In aggressive mode, UDLD also detects unidirectional links caused by one-way traffic on fiber-optic and twisted-pair links and by incorrectly connected interfaces on fiber-optic links. For information about enabling UDLD on the switch module, see the “Understanding UDLD” section in the software configuration guide.

Cisco Catalyst Blade Switch 3120 for HP Hardware Installation Guide

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