In STP, which ports on the root bridge are in the forwarding state?

In Spanning Tree Protocol (STP), the designated ports are the ports on a network bridge or switch that have been selected to forward data towards the root bridge. When a switch becomes the root bridge, all its ports are considered in a forwarding state, but specifically, the designated ports on the root bridge are responsible for forwarding traffic toward other switches in the network.

Designated ports are critical because they are the ones through which the best path to the root bridge is achieved for a given network segment. They are selected at each network segment based on having the lowest path cost to the root bridge. Since the root bridge serves as the central point in STP, all designated ports on it ensure that there is no loop in the network and that data can flow freely in the correct direction.

The other options refer to states or roles that do not relate directly to the forwarding capability on the root bridge itself. Blocking ports do not forward frames, root ports exist on non-root bridges to point toward the root, and non-designated ports also do not forward frames. By understanding that only designated ports on a root bridge are responsible for forwarding, you can see why this option is the correct choice in the context of STP operations.