PortFast causes a Layer 2 LAN access port to enter the forwarding state immediately, bypassing the listening and learning states. When configured for PortFast, a port is still running Spanning Tree Protocol and can immediately transition to the blocking state, if necessary. PortFast should be used only when connecting a single end station to the port. It can be enabled on trunk ports.
UplinkFast
UplinkFast provides fast convergence after a direct link failure. UplinkFast cannot be configured on individual VLANs; it is configured on all VLANs of a LAN switch. It is most useful when configured on the uplink ports of closet switches connecting to distribution switches. This mechanism is enabled when RSTP is enabled on a switch.
BackboneFast
BackboneFast provides fast failover when an indirect link failure occurs. It is initiated when a root port or blocked port on a network device receives inferior BPDUs from its designated bridge. It is configured on distribution and core switches. As with UplinkFast, this mechanism does not need to be enabled when RSTP is configured.
Loop Guard
Loop Guard helps prevent bridging loops that could occur because of a unidirectional link failure on a point-to-point link. It detects root ports and blocked ports and ensures that they keep receiving BPDUs from the designated port on the segment. When Loop Guard is enabled, if a root or blocked port stops receiving BPDUs from its designated port, it transitions to the loop-inconsistent blocking state.
Loop Guard can be enabled on a per-port basis. It must be configured on point-to-point links only. When Loop Guard is enabled, it is automatically applied to all active instances or VLANs to which that port belongs. When enabled on an EtherChannel (link bundle) and the first link becomes unidirectional, it blocks the entire channel until the affected port is removed from the channel. Loop Guard cannot be enabled on PortFast ports, dynamic VLAN ports, or Root Guard–enabled switches. It does not affect UplinkFast or BackboneFast operation.
Root Guard
Root Guard prevents a port from becoming a root port or blocked port. When a Root Guard port receives a superior BPDU, the port immediately goes to the root-inconsistent (blocked) state. Root Guard is configured on access switches so that they do not become a root of the spanning tree.
BPDU Guard
BPDU Guard shuts down a port that receives a BPDU, regardless of PortFast configuration. In a valid configuration, PortFast-enabled ports do not receive BPDUs. Reception of a BPDU by a PortFast-enabled port signals an invalid configuration.