Q: What are all of these Cisco extensions to Spanning Tree protocol (STP)?

A:

Backbone Fast Convergence

Provides fast convergence after a spanning-tree topology change caused by indirect link failures.

Loop Guard

The loop guard feature checks that a root port or an alternate root port is receiving BPDUs. If a port is not receiving BPDUs, the loop guard feature puts the port into an inconsistent state, isolating the failure and letting spanning tree converge to a stable topology until the port starts receiving BPDUs again.

Portfast

STP PortFast causes a Layer 2 LAN interface configured as an access port to enter the forwarding state immediately, bypassing the listening and learning states.

Portfast BPDU Guard

Provides a means to shut the port down when any received BPDUs are detected.

Root Guard

The STP root guard feature prevents a port from becoming root port or blocked port. If a port configured for root guard receives a superior BPDU, the port immediately goes to the root-inconsistent (blocked) state.

Uplink Fast Convergence

Uplink Fast Convergence provides rapid switchover to a redundant uplink for wiring closet switches when the spanning-tree root port fails or when the spanning-tree topology is recalculated.

Uplink Load Balancing

Uplink Load Balancing by VLAN enables traffic load balancing across uplinks by providing direct control over the spanning-tree port cost for VLANs on a trunking port.