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Troubleshooting
This chapter describes how to identify and resolve software problems related to the Cisco IOS software on the switch.
Depending on the nature of the problem, you can use the command-line interface (CLI), Network Assistant or Device
Manager to identify and solve problems.
For additional troubleshooting information, such as LED descriptions, see the Hardware Installation Guide.
Information for Troubleshooting
Autonegotiation Mismatches Prevention
The IEEE 802.3ab autonegotiation protocol manages the switch settings for speed (10 Mb/s, 100 Mb/s, and 1000 Mb/s,
excluding SFP module ports) and duplex (half or full). There are situations when this protocol can incorrectly align these
settings, reducing performance. A mismatch occurs under these circumstances:
A manually set speed or duplex parameter is different from the manually set speed or duplex parameter on the
connected port.
A port is set to autonegotiate, and the connected port is set to full duplex with no autonegotiation.
To maximize switch performance and ensure a link, follow one of these guidelines when changing the settings for duplex
and speed:
Let both ports autonegotiate both speed and duplex.
Manually set the speed and duplex parameters for the ports on both ends of the connection.
Note: If a remote device does not autonegotiate, configure the duplex settings on the two ports to match. The speed
parameter can adjust itself even if the connected port does not autonegotiate.
SFP Module Security and Identification
Cisco small form-factor pluggable (SFP) modules have a serial EEPROM that contains the module serial number, the
vendor name and ID, a unique security code, and cyclic redundancy check (CRC). When an SFP module is inserted in
the switch, the switch software reads the EEPROM to verify the serial number, vendor name and vendor ID, and
recompute the security code and CRC. If the serial number, the vendor name or vendor ID, the security code, or CRC is
invalid, the software generates a security error message and places the interface in an error-disabled state.
Note: The security error message references the GBIC_SECURITY facility. The switch supports SFP modules and does
not support GBIC modules. Although the error message text refers to GBIC interfaces and modules, the security
messages actually refer to the SFP modules and module interfaces.
If you are using a non-Cisco SFP module, remove the SFP module from the switch, and replace it with a Cisco module.
After inserting a Cisco SFP module, use the errdisable recovery cause gbic-invalid global configuration command to
verify the port status, and enter a time interval for recovering from the error-disabled state. After the elapsed interval,
the switch brings the interface out of the error-disabled state and retries the operation.
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