IN this network diagram R3 is root switch and in switch R1 f1/0 is root port and f1/1 is in blocking state.
Now if I want to make port f1/1 in switch R1 as root port I have to change (lower) the port priority of f1/1 on switch R2.
why changing the port priority of f1/1 on switch R2 only doesn'tmake it root port ?
why it is calculating the port priority of R2 .
When R1 is deciding which port to block it will look to see which one of its ports "received" the best information. If cost is equal the tie breaker will go down to port priority. Lower is better. So when you change the port priority of R2 f1/1, R1's fa1/1 receive a better metric than the one its receiving on Fa1/0 so it decides to forward out Fa1/1 and block Fa0/0