BPDU Filter

BPDU Filter is a Spanning Tree feature that prevents ports from sending or receiving BPDUs, protecting the topology from unwanted exchanges. This lesson explains when to use BPDU Filter, how to configure it, and why it matters for securing STP.

  • By default, ports connected to end-user devices (PCs, printers) send BPDUs as part of the Spanning Tree Protocol (STP) process.

    BPDU Filter CCNA illustration showing a switch sending BPDUs every 2 seconds to end-user devices before filtering is applied

    Figure 1 – Switches send BPDUs every 2 seconds by default

    However, in most cases, sending BPDUs on these ports is unnecessary and can expose sensitive STP topology information.

    BPDU Filter is an STP feature that disables sending and receiving of BPDUs on ports, enhancing security and preventing unwanted BPDU exchanges.

    BPDU Filter CCNA example showing a switch preventing BPDU transmission to end-user devices for enhanced STP security

    Figure 2 – BPDU Filter blocks both sending and receiving of BPDUs

    Real-World Use Case

    BPDU Filter is especially useful in scenarios like company mergers, where two networks with separate STP topologies are interconnected.

    BPDU Filter ensures that BPDUs are not exchanged between the different STP topology preserving their independent spanning tree configurations.

    BPDU Filter CCNA example showing two separate STP topologies preventing BPDU exchanges to maintain independent spanning tree configurations

    Figure 3 – BPDU Filter prevents STP topology exchanges between two networks

    This ensures that each network maintains its own spanning tree configuration without sharing or disrupting the other’s topology.

    Answer the question below

    What does BPDU Filter block on a port?