PortFast and BPDUs

PortFast and BPDUs
Some switches support an addition to PortFast called BPDUGuard. There is never a guarantee that
someone won’t add a switch at their desk. Then, for redundancy, they also connect that switch to
the LAN drop at their neighbor’s desk. Now assume that you enable PortFast on that port. Congratulations,
you now have a spanning tree loop!
BPDUGuard is a feature that can be set on many switches that enable PortFast. It monitors for
BPDUs on that port. If a BPDU arrives, the switch shuts down the port, placing it in the errdisable
state, and generates a status message.