DELL N3000 User Manual

Configuring the Spanning Tree Protocol

The Dell Networking series switches support the following optional STP 

features:

• BPDU flooding
• PortFast
• BPDU filtering
• Root guard
• Loop guard
• BPDU protection

The BPDU flooding feature determines the behavior of the switch when it 

receives a BPDU on a port that is disabled for spanning tree. If BPDU 

flooding is configured, the switch will flood the received BPDU to all the 

ports on the switch which are similarly disabled for spanning tree.

The PortFast feature reduces the STP convergence time by allowing edge 

ports that are connected to end devices (such as a desktop computer, printer, 

or file server) to transition to the forwarding state without going through the 

listening and learning states.

Ports that have the PortFast feature enabled continue to transmit BPDUs. 

The BPDU filtering feature prevents PortFast-enabled ports from sending 

BPDUs. 
If BPDU filtering is configured globally on the switch, the feature is 

automatically enabled on all operational PortFast-enabled ports. These ports 

are typically connected to hosts that drop BPDUs. However, if an operational 

edge port receives a BPDU, the BPDU filtering feature disables PortFast and 

allows the port to participate in the spanning tree calculation.
Enabling BPDU filtering on a specific port prevents the port from sending 

BPDUs and allows the port to drop any BPDUs it receives.