Per-VLAN Spanning Tree (PVST) and Per-VLAN Spanning Tree Plus (PVST+)

The type of a single instance Spanning Tree Protocol (STP) is known as Common Spanning Tree (CST).

Delay in receiving BPDUs is common  in large switched Common Spanning Tree (CST) networks. The delay in receiving BPDUs can cause problems like convergence time problems. Per-VLAN Spanning Tree (PVST) is a solution for these problems. Per-VLAN Spanning Tree (PVST) is a Cisco proprietary Spanning Tree Protocol (STP) which operates a separate instance of Spanning Tree Protocol (STP) for each individual VLAN. A separate instance of Spanning Tree Protocol (STP) for each VLAN helps VLAN to be configured independently and also can perform better. Per-VLAN Spanning Tree (PVST) requires Inter-Switch Link (ISL).

Per-VLAN Spanning Tree+ (PVST+) is an extension of the PVST standard. Per-VLAN Spanning Tree+ (PVST+) allows interoperability between CST and PVST in Cisco switches and support the IEEE 802.1Q standard.