Types of STP
Like many networking standards, there are many types or variants of STP. These include:
These are public or industrial specification created by the IEEE. Some of these STP types are Cisco proprietary and others are IEEE standards.
You will learn more details on some of these STP variants, but to get started you need to have a general knowledge of what the key STP variants are. Below, is a brief description of the key Cisco and IEEE STP variants.
Per-VLAN Spanning Tree Protocol (PVST) – Maintains a spanning-tree instance for each VLAN configured in the network. It uses the Cisco proprietary ISL trunking protocol that allows a VLAN trunk to be forwarding for some VLANs while blocking for other VLANs. Because PVST treats each VLAN as a separate network, it can load balance traffic at Layer 2 by forwarding some VLANs on one trunk and other VLANs on another trunk without causing a loop. For PVST, Cisco developed a number of proprietary extensions to the original IEEE 802.1D STP, such as BackboneFast, UplinkFast, and PortFast.
To learn more about these extensions, visit:
Configuring Spanning Tree PortFast, BPDU Guard, BPDU Filter, UplinkFast,
Per-VLAN Spanning Tree Protocol Plus (PVST+) – Cisco developed PVST+ to provide support for IEEE 802.1Q trunking. PVST+ provides the same functionality as PVST, including the Cisco proprietary STP extensions. PVST+ is not supported on non-Cisco devices. PVST+ includes the PortFast enhancement called BPDU guard, and root guard.
To learn more about BPDU guard, visit:
Spanning Tree PortFast BPDU Guard Enhancement
To learn more about root guard, visit:
Spanning Tree Protocol Root Guard Enhancement
Rapid Per-VLAN Spanning Tree Protocol (rapid PVST+) – Based on the IEEE 802.1w standard and has a faster convergence than STP (standard 802.1D). Rapid PVST+ includes Cisco-proprietary extensions such as BackboneFast, UplinkFast, and PortFast.
Rapid Spanning Tree Protocol (RSTP) – First introduced in 1982 as an evolution of STP (802.1D standard). It provides faster spanning-tree convergence after a topology change. RSTP implements the Cisco-proprietary STP extensions, BackboneFast, UplinkFast, and PortFast, into the public standard. As of 2004, the IEEE has incorporated RSTP into 802.1D, identifying the specification as IEEE 802.1D-2004. So when you hear STP, think RSTP.
Multiple STP (MSTP) – Enables multiple VLANs to be mapped to the same spanning-tree instance, reducing the number of instances needed to support a large number of VLANs. MSTP was inspired by the Cisco-proprietary Multiple Instances STP (MISTP) and is an evolution of STP and RSTP. It was introduced in IEEE 802.1s as amendment to 802.1Q, 1998 edition. Standard IEEE 802.1Q-2003 now includes MSTP. MSTP provides for multiple forwarding paths for data traffic and enables load balancing.
To learn more about MSTP, visit: