Which of the following statements about the Backup port in the RSTP protocol is correct?
A . Backup port as a backup of the designated port, providing another backup path from the root bridge to the corresponding network segment
B . Backup port not only forwards user traffic but also learns MAC address
C . Backup port does not forward user traffic but learns MAC address
D . Backup port provides another switchable path from the designated bridge to the root as the backup port of the root port
Answer: A