Core issue
The undersize frames notification on the Cisco Catalyst Express 500 switch means that the switch is receiving frames of 61-64 bytes in size on that interface. However, it continues to forward the traffic. This error does not affect the performance of the switch.
The switch turns on the alert light for any notification when Cisco IOS code 12.2.25.FY.
Resolution
This issue is resolved in Cisco IOS version 12.2.25.SEG and later, in which the software only turns on the light for critical errors. This version is available for download on the LAN Switching Software page.