Description: The RSTP provides rapid convergence of the spanning tree by assigning one of these port roles to individual ports and by determining the active topology.

Root port Provides the best path (lowest cost) when the switch forwards packets to the root switch.

Designated port Connects to the designated switch, which incurs the lowest path cost when forwarding packets from that LAN to the root switch. The port through which the designated switch is attached to the LAN is called the designated port.

Alternate port Offers an alternate path toward the root switch to that provided by the current root port.

Backup port Acts as a backup for the path provided by a designated port toward the leaves of the spanning tree. A backup port can exist only when two ports are connected together in a loopback by a point-to-point link or when a switch has two or more connections to a shared LAN segment.

Disabled port Has no role within the operation of the spanning tree.

A port with the root or a designated port role is included in the active topology. A port with the alternate or backup port role is excluded from the active topology.