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Catalyst 2940 Switch Software Configuration Guide
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Chapter 12 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
Caution Configure Port Fast only on ports 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 port without also enabling the Port Fast feature. This command prevents the port
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.
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.
Enabling UplinkFast for Use with Redundant Links (Optional)
UplinkFast cannot be enabled on VLANs that have been configured for switch priority. To enable
UplinkFast on a VLAN with switch priority configured, first restore the switch priority on the VLAN to
the default value by using the no spanning-tree vlan vlan-id priority global configuration command.
Note When you enable UplinkFast, it affects all VLANs on the switch. You cannot configure UplinkFast on
an individual VLAN.
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 Enter interface configuration mode, and specify the interface
connected to an end station.
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.