Step 3: Correct the Problem

Note: EtherChannel and STP must interoperate

For this reason, the order in which EtherChannel-related commands are entered is important, which is why you see interface Port-Channel 1 removed and then re-added with the channel-group command, as opposed to directly changed

If one tries to change the configuration directly, STP errors cause the associated ports to go into blocking or errdisabled state

To correct the issue, the PAgP mode on the EtherChannel is changed to desirable