MSTP

MSTP overcomes the following STP, RSTP, and PVST limitations:

• STP limitations—STP does not support rapid state transition of ports. A newly elected port must wait twice the forward delay time before it transits to the forwarding state.

• RSTP limitations—Although RSTP enables faster network convergence than STP, RSTP fails to provide load balancing among VLANs. As with STP, all RSTP bridges in a LAN share one spanning tree and forward packets from all VLANs along this spanning tree.

• PVST limitations—Because each VLAN has its spanning tree, the amount of PVST BPDUs is proportional to the number of VLANs on a trunk or hybrid port. When the trunk or hybrid port permits too many VLANs, both resources and calculations for maintaining the VLAN spanning trees increase dramatically. If a status change occurs on the trunk or hybrid port that permits multiple VLANs, the device CPU will be overburdened with recalculating the affected spanning trees. As a result, network performance is degraded.