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Catalyst 3750 Metro Switch Software Configuration Guide
78-15870-01
Chapter 16 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
Enabling BPDU Filtering
When you globally enable BPDU filtering on Port Fast-enabled interfaces, it prevents interfaces that are
in a Port Fast-operational state from sending or receiving BPDUs. The interfaces still send a few BPDUs
at link-up before the switch begins to filter outbound BPDUs. You should globally enable BPDU filtering
on a switch so that hosts connected to these interfaces do not receive BPDUs. If a BPDU is received on
a Port Fast-enabled interface, the interface loses its Port Fast-operational status, and BPDU filtering is
disabled.
Caution Configure Port Fast only on interfaces that connect to end stations; otherwise, an accidental topology
loop could cause a data packet loop and disrupt switch and network operation.
You can also use the spanning-tree bpdufilter enable interface configuration command to enable
BPDU filtering on any interface without also enabling the Port Fast feature. This command prevents the
interface from sending or receiving BPDUs.
Caution Enabling BPDU filtering on an interface is the same as disabling spanning tree on it and can result in
spanning-tree loops.
You can enable the BPDU filtering feature if your switch is running PVST+, rapid PVST+, or MSTP.
Beginning in privileged EXEC mode, follow these steps to globally enable the BPDU filtering feature.
This procedure is optional.
To disable BPDU filtering, use the no spanning-tree portfast bpdufilter default global configuration
command.
You can override the setting of the no spanning-tree portfast bpdufilter default global configuration
command by using the spanning-tree bpdufilter enable interface configuration command.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
spanning-tree portfast bpdufilter default Globally enable BPDU filtering.
By default, BPDU filtering is disabled.
Step 3
interface interface-id Specify the interface connected to an end station, and enter
interface configuration mode.
Step 4
spanning-tree portfast Enable the Port Fast feature.
Step 5
end Return to privileged EXEC mode.
Step 6
show running-config Verify your entries.
Step 7
copy running-config startup-config (Optional) Save your entries in the configuration file.
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