Hello Dean,

this command disables some form of optimization in sending STP BPDUs out of a switch so that it will propagate the BPDU received over the root port out of all non-blocking ports without trying to perform any action in order to reduce the number of sent BPDUs (this is just an example).

I tried to find the command in the command reference for c4500 12.2(46)SG and c6500 12.2(33)SXH without finding it.

From some search this command can be related to MST 802.1s.

Hope to help

Giuseppe