These messages indicate that the switch forwarding engine is getting an IPX packet that is less than the minimum length allowed, and dropping it. In older code (pre-7.x, pre 12.1(13E)), the packet was silently dropped and counted in the forwarding engine stats. In newer code (7.x and above,12.1(13E) ), this message is recorded in the syslog once every 30 minutes.There is no effect on the switch side. The switch side is dropping the bad packet, which would have been dropped by the receiving device consequently.The only concern is that there is a device sending bad packets (possibly due to a bad NIC driver, NIC driver bug or bad application, and so on).
The Supervisor Engine does not keep track of the source-ip, mac address or port of the device that is sending the bad packets. It can not because that is a limitation of the hardware. That makes tracking the source of the bad packet down difficult. These errored packets are not copied to a SPAN session so SPAN and sniffing might not be very useful. In such cases, the only way to catch the packets would be to insert a hub between the device and the switch. Another suggestion has been to shut down ports to see if the error message goes away. Locating the source of these packets is not an easy task. Ultimately, this is not a problem with the switch, so you can rest assured that the switch is not impacted in any way.
If you prefer, you can disable these error messages, by using the "set errordetection portcounters disable" command on the switch.
This error is also documented on CCO at
http://www.cisco.com/warp/public/473/186.html#subtopic1k
