BPDU Filtering Applied Globally versus Per-Port
BPDU filtering
can be configured globally or in individual PortFast enabled ports.

When
enabled globally, it has these attributes:
- It affects all operational PortFast ports on a switch that do not have BPDU
filtering configured on the individual port.
- If BPDUs are seen, the port looses its PortFast Status, BPDU filtering is
disabled and STP sends and receives BPDUs on the port as any other STP port on
the switch.
- Upon startup, the port transmits ten BPDUs. If this port receives any BPDUs
during that time, PortFast and PortFast BPDU filtering are disabled.
When enabled on an individual port, it has these attributes:
- Ignores all BPDUs received
- Sends no BPDUs
 |
CAUTION:
Explicit configuration of PortFast BPDU Filtering on a port not
connected to a host station can result in bridging loops. The port ignores any
incoming BPDU and changes to the forwarding state. This does not occur when
PortFast BPDU filtering is enabled globally.
|
|
|
The BPDU Filtering Results table lists the possible combinations
that result from configuring BPDU filtering globally and on individual ports
and on the same switch.

Configuring BPDU Filtering
To enable PortFast BPDU filtering
globally on the switch, enter this command:
Switch(config)#spanning-tree portfast bpdufilter
default
To enable PortFast BPDU filtering on a specific switch port, enter this
command:
Switch(config-if)#spanning-tree bpdufilter
enable
Verifying BPDU Filtering
To verify
the configuration on the switch, enter this command:
Switch#show spanning-tree summary
totals
To verify the configuration on a specific port, enter the command to see the
associated output.
