In a 6509, 7609 or any Chassis based Cisco switch, to determine where the switch forwards a Source and Destination pair to an actual port in a Port-channel/Etherchannel do the following commands:
Note: Doesn’t apply to Nexus switches.
First enter console for switch:
Switch# remote login
Trying Switch ...
Then enter the following command:
Switch-SP# test etherchannel load-balance
Would select Gi2/
Based on the hash computation, the switch forwards traffic of the Src Dst pair to port Gi2/1.
This is a good tool to use if for some reason a particular port is dropping packets between the src and dst pairs.