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Understanding How PortFast BPDU Filtering Works
Understanding How PortFast BPDU Filtering Works
BPDU filtering allows you to avoid transmitting BPDUs on PortFast-enabled ports that are connected to
an end system. When you enable PortFast on the switch, spanning tree places ports in the forwarding
state immediately, instead of going through the listening, learning, and forwarding states.
By default, spanning tree sends BPDUs from all ports regardless of whether PortFast is enabled. BDPU
filtering is on a per-switch basis; after you enable BPDU filtering, it applies to all PortFast-enabled ports
on the switch.
Configuring PortFast BPDU Filtering
These sections describe how to configure PortFast BPDU filtering on the switch:
•
•
Enabling PortFast BPDU Filtering
Note
Although you can configure PortFast on an individual port, you configure the PortFast BPDU filter
option globally. When you disable PortFast on a port, PortFast BPDU filter becomes inactive for that
port.
To enable PortFast BPDU filtering on a nontrunking switch port, perform this task in privileged mode:
Task
Step 1
Enable PortFast BPDU filtering on the switch.
Step 2
Verify the PortFast BPDU filtering setting.
This example shows how to enable PortFast BPDU filtering on the switch and verify the configuration
in Per VLAN Spanning Tree+ (PVST+) mode:
Note
For additional PVST+ information, see
Console> (enable) set spantree portfast bpdu-filter enable
Usage: set spantree portfast <mod/port> <enable|disable>
Spantree portfast bpdu-filter enabled on this switch.
Console> (enable) show spantree portfast
Portfast BPDU guard is disabled.
Portfast BPDU filter is disabled.
Vlan
----- -------- --------- -------- ---------- ----------
Software Configuration Guide—Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4
8-6
Chapter 8
Enabling PortFast BPDU Filtering, page 8-6
Disabling PortFast BPDU Filtering, page 8-7
set spantree portfast bpdu-guard <enable|disable>
set spantree portfast bpdu-filter <enable|disable>
Blocking Listening Learning Forwarding STP Active
Configuring Spanning Tree PortFast, UplinkFast, and BackboneFast, and Loop Guard
Command
set spantree portfast bpdu-filter enable
show spantree summary
show spantree portfast
Chapter 7, "Configuring Spanning Tree."
78-12647-02
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