Core issue
While a frame is being transmitted, the local buffer of the controller chip local buffer receives insufficient data. The data could not be transferred to the chip fast enough to keep pace with output rate. Normally, such a condition is temporary, depending on transient peak loads within the system.
The issue occurs when an excessive amount of traffic is processed by the FastEthernet interface. The error message is received When traffic level reaches about 2.5 Mb. This traffic level constrain is due to hardware limitation. Because of this there is a chance for the device connected to the catalyst switch to drop packets.
Resolution
Normally, the system recovers automatically. No action is required.
If the switch is overwhelming the Ethernet interface, check the speed and duplex settings. You can also use a sniffer program to analyze packets coming in and out of the router fast Ethernet interface.
To avoid packet drops on the device connected to the catalyst switch, issue the command ip cef on the fast ethernet interface of the device connected to the switch.
For further assistance, open a case with Cisco Technical Support.
Problem frequency
Intermittent
Device connected to switch
External router
Error message
%AMDP2_FE-3-UNDERFLO
Show interface
underruns
