Spanning-Tree Enhancements

Portfast

Immediately change a port into a forwarding port. Can be used for ports that are connected to end devices. Should always be paired with BPDU guard. With BPDU guard enabled on a switch, if that switch received a BPDU from a portfast port, it will shutdown the port

PortFast Configuration
go to the interface configuration level

spanning-tree portfast

BPDU Guard configuration
in the global configuration level

spanning-tree portfast bpduguard

There’s another feature other than BPDUguard, called BPDU-Filter, if a BPDU was received by the switch on a portfast port, the BPDU will just be ignored.

UplinkFast

Not much used anymore. Uplink fast provides a way to make a blocked port change into a forwarding port in case that the root port is down.

UpLinkFast Configuration:
go to the interface configuration level

spanning-tree uplinkfast

BackBone Fast

When a root port of a switch is down, there could be a chance the switch thinks that the root bridge is down, while it’s actually not. When this happens, the switch will send BPDUs with its own switch priority and and MAC address as the root bridge, if this ever happens and received by another switch on which the Backbone fast is enabled, this switch will pro-actively tell the switch that assume it is the root bridge that the root bridge is still alive by sending a BPDU back to that switch with the real Root Bridge ID.

BackBoneFast Configuration:
go to the interface configuration level

spanning-tree backbonefast