Out of the six ports that are connected by cable, the port for which the loop is most quickly detected is the one that is blocked.
○When detected in port1.2 of switch #A
port1.1: Detected, port1.2: Blocking
○When detected in port1.4 of switch #B
port1.3: Detected, port1.4: Blocking
○When detected in port1.6 of switch #C
port1.5: Detected, port1.6: Blocking