612 Configuring the Spanning Tree ProtocolWhat are the Optional STP Features?The PowerConnect 8000-series and 8100-series switches support thefollowing optional STP features:• BPDU flooding• PortFast• BPDU filtering• Root guard• Loop guard• BPDU protectionBPDU FloodingThe BPDU flooding feature determines the behavior of the switch when itreceives a BPDU on a port that is disabled for spanning tree. If BPDUflooding is configured, the switch will flood the received BPDU to all theports on the switch which are similarly disabled for spanning tree.Port FastThe PortFast feature reduces the STP convergence time by allowing edgeports that are connected to end devices (such as a desktop computer, printer,or file server) to transition to the forwarding state without going through thelistening and learning states.BPDU FilteringPorts that have the PortFast feature enabled continue to transmit BPDUs.The BPDU filtering feature prevents PortFast-enabled ports from sendingBPDUs.If BPDU filtering is configured globally on the switch, the feature isautomatically enabled on all operational PortFast-enabled ports. These portsare typically connected to hosts that drop BPDUs. However, if an operationaledge port receives a BPDU, the BPDU filtering feature disables PortFast andallows the port to participate in the spanning-tree calculation.Enabling BPDU filtering on a specific port prevents the port from sendingBPDUs and allows the port to drop any BPDUs it receives.
