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Forum Replies

  1. Hi Rene,
    What happens when Portfast is enabled on a port but BPDU filter is not globally enabled and the port receives a BPDU.


  2. Thanks Andrew. I have one more question, What is the real use of BPDU filter command in a Global mode, if a normal portfast can achieve the same functionality. Why do we need to enable BPDU filter at the global level and what enhancement does it provide at the global level. BPDU filter lesson says.

    BPDUfilter can be configured globally or on the interface level and there’s a difference:

    Global: if you enable BPDUfilter globally then any interface with portfast enabled will not send or receive any BPDUs. When you receive a BPDU on a portfast enabled interface th

    ... Continue reading in our forum

  3. Hello Tejpal

    What actually happens when a portfast configured port receives a BPDU actually depends on the configuration.

    1. In simple STP (IEEE802.1D), a portfast port will be reset back to a normal port participating in STP if BDPUs arrive on the port. If a physical L2 loop is created on such a port, it will result in a temporary L2 loop until STP reconverges. This is why you will see this warning when configuring portfast (notice the word “temporary”:

       %Warning: portfast should only be enabled on ports connected to a single
        host. Connecting hubs, concentr
    ... Continue reading in our forum

  4. Hello Swapnil

    If a situation like this happens, the port that is configured with portfast will receive a BPDU. What happens next depends on how the port is configured. Take a look at the previous post above to see more details.

    In general it is best practice to enable portfast only on ports that have end devices connected to them and not other switches.

    I hope this has been helpful!


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