Enabling BPDU Filtering
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Enabling and Verifying BPDU Filtering |
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r„.„„,„m |
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Switch(config)#spanning-tree portfast bpdufilter default |
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• Enables BPDU filtering |
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Switch#show spanning-tree summary totals |
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• Displays BPDU filtering configuration information |
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Switch#show spanning-tree summary totals Root bridge for:VLAN0010 EtherChannel misconfiguration guard is enabled Extended system ID is disabled Portfast is enabled by default PortFast BPDU Guard is disabled by default Portfast BPDU Filter is enabled by default Loopguard is disabled by default UplinkFast is disabled BackboneFast is disabled Pathcost method used is long |
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Name |
Blocking Listening Learning Forwarding STP Active |
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2 vlans |
0 0 0 3 3 |
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© 2004, Cisco Systems, Inc. All rights reserve |
d. BCMSN v2.1—4-49 |
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PortFast BPDU filtering 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.
When you enable PortFast BPDU filtering globally and set the port configuration as the default for PortFast BPDU filtering, PortFast enables or disables PortFast BPDU filtering.
Caution Explicit configuration of PortFast BPDU filtering on a port that is not connected to a host can result in bridging loops. This is because the port ignores any incoming BPDU and changes its role to the forwarding state.
If the port configuration is not set to default, the PortFast configuration will not affect PortFast BPDU filtering. PortFast BPDU filtering allows access ports to move directly to the forwarding state as soon as the end hosts are connected. The table lists all the possible PortFast BPDU filtering combinations.
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Per-Port Configuration |
Global Configuration |
PortFast State |
PortFast BPDU Filtering State |
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Default |
Enable |
Enable |
Enable |
|
Default |
Enable |
Disable |
Disable |
|
Default |
Disable |
Not applicable |
Disable |
|
Disable |
Not applicable |
Not applicable |
Disable |
|
Enable |
Not applicable |
Not applicable |
Enable |
The port transmits at least ten BPDUs. If this port receives any BPDUs, PortFast and PortFast BPDU filtering are disabled.
To enable PortFast BPDU filtering globally on the switch, enter this command:
Switch(config)#spanning-tree portfast bpdufilter default To verify the configuration, enter this command:
Switch#show spanning-tree summary totals
Continue reading here: Enabling BPDU Skewing Detection
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