A Supervisor 720 (Sup720) running 12.2(17d)SXB1 that acts as a PE could display this error message, followed by a traceback:
%MSFC2-3-TOOBIG: Attempt to send giant packet on GigabitEthernet9/1 (1574 bytes from 83226C2, max allowed 1572)
This error message means that an attempt was made to send giant or oversized packet on [chars] ([dec] bytes from [hex], max allowed [dec]). This occurs when Multi Layer Switching (MLS) or Layer 3 switching does not fragment packets in the event of messages larger than 1580 bytes.
This problem is identified in Cisco bug ID CSCee95708.
The workaround for this issue is to increase the MTU size on the affected interface. In order to adjust the maximum packet size or MTU size, issue the mtu command. After the MTU size is configured larger than 1580 bytes, this error message can be avoided.
Alternatively, in order to resolve this problem, upgrade the Cisco IOS Software on the switch to the 12.2(18)SXD and later releases, available for download from the IOS Upgrade Planner.