Difference between spanning-tree portfast bpduguard default and spanning-tree bpdufilter

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Understanding How PortFast BPDU Filtering Works

Release 12.1(13)E and later releases support PortFast BPDU filtering, which allows the administrator to prevent the system from sending or even receiving BPDUs on specified ports.

When configured globally, PortFast BPDU filtering applies to all operational PortFast ports. Ports in an operational PortFast state are supposed to be connected to hosts, that typically drop BPDUs. If an operational PortFast port receives a BPDU, it immediately loses its operational PortFast status. In that case, PortFast BPDU filtering is disabled on this port and STP resumes sending BPDUs on this port.

PortFast BPDU filtering can also be configured on a per-port basis. When PortFast BPDU filtering is explicitly configured on a port, it does not send any BPDUs and drops all BPDUs it receives.


Caution Explicate configuring PortFast BPDU filtering on a port that is not connected to a host can result in bridging loops as the port will ignore any BPDU it receives and go to forwarding.
When you enable PortFast BPDU filtering globally and set the port configuration as the default for PortFast BPDU filtering (see the "Enabling PortFast BPDU Filtering" section), then PortFast enables or disables PortFast BPDU filtering.

If the port configuration is not set to default, then the PortFast configuration will not affect PortFast BPDU filtering. Table 16-1 lists all the possible PortFast BPDU filtering combinations. PortFast BPDU filtering allows access ports to move directly to the forwarding state as soon as the end hosts are connected.

Table 16-1 PortFast BPDU Filtering Port Configurations

Per-Port Configuration
Global Configuration
PortFast State
PortFast BPDU Filtering State
Default

Enable

Enable

Enable1

Default

Enable

Disable

Disable

Default

Disable

Not applicable

Disable

Disable

Not applicable

Not applicable

Disable

Enable

Not applicable

Not applicable

Enable

1 The port transmits at least 10 BPDUs. If this port receives any BPDUs, then PortFast and PortFast BPDU filtering are disabled.