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Chapter 3
Troubleshooting
Transceiver Issues
Use only Cisco X2 transceiver 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. Evaluate these items:
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Port and Interface Settings
An obvious but sometimes overlooked cause of port connectivity failure is a disabled port. Verify that
the port or interface is not disabled or powered down for some reason. If a port or interface is manually
shut down on one side of the link or the other side, the link does not come up until you re-enable the
port. Use the show interfaces privileged EXEC command to verify the port or interface error-disabled,
disabled, or shutdown status on both sides of the connection. If needed, re-enable the port or the
interface.
Ping End Device
Test the end device by pinging 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 see 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 look like port or interface
problems. In this situation, the switch module bandwidth is used over and over again by the same frames,
leaving little room for legitimate traffic.
Loops can be caused by a unidirectional link. A unidirectional link occurs whenever the traffic sent by
the switch module is received by its neighbor, but the traffic from the neighbor is not received by the
switch module. A broken fiber-optic cable, other cabling, or a port issue could cause this one-way
communication.
You can enable UniDirectional Link Detection (UDLD) on the switch module to help identify
difficult-to-find unidirectional link problems. UDLD supports two modes of operation: normal (the
default) and aggressive. In normal mode, UDLD detects unidirectional links due to misconnected
interfaces on fiber-optic connections. In aggressive mode, UDLD also detects unidirectional links due
to one-way traffic on fiber-optic and twisted-pair links and due to misconnected interfaces on fiber-optic
links. For information about enabling UDLD on the switch module, see the "Understanding UDLD"
section in the software configuration guide for this release.
OL-12192-01
Bad or wrong X2 transceiver module. Exchange suspect module with known good module. Verify
that the module is supported on this platform. (The switch module release notes on Cisco.com list
the X2 modules that the switch module supports.)
Use the show interfaces privileged EXEC command to verify the port or module error-disabled,
disabled, or shutdown status. Re-enable the port if needed.
Make sure that all fiber connections are properly cleaned and securely connected.
For CX4 module connections, make sure that cable routing does not violate the minimum allowed
cable-bend radius. See the module documentation for specific cabling requirements.
For LX4 modules, we recommend a mode conditioning patch for MMF applications.
Catalyst Switch Module 3110G, 3110X, and 3012 for IBM BladeCenter Hardware Installation Guide
Diagnosing Problems
3-3
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