STP BPDU Guard

BPDU Guard is a feature of STP that shuts down a port configured with PortFast in the event that a BPDU is detected. This protects against employees bringing in their own switches, connecting them to their network jacks in their offices, possibly causing their “rogue” switches to become a root bridge. Only hosts should be connected to PortFast ports, and this mechanism protects against such situations.

For additional STP fine tuning features, take a look at STP fine tuning the spanning tree protocol.

Links:

https://networklessons.com/spanning-tree/spanning-tree-bpduguard

https://networklessons.com/spanning-tree/cisco-portfast-configuration

https://www.ciscopress.com/articles/article.asp?p=2995351&seqNum=3