Understanding Bpdu Guard - Cisco WS-C3550-12G Software Configuration Manual

Chapter 10 Configuring STP
Figure 10-4 Port Fast-Enabled Ports
Catalyst 3550

Understanding BPDU Guard

When the BPDU guard feature is enabled on the switch, STP shuts down Port Fast-enabled interfaces
that receive BPDUs rather than putting them into the blocking state. In a valid configuration, Port
Fast-enabled interfaces do not receive BPDUs. Receipt of a BPDU by a Port Fast-enabled interface
means an invalid configuration, such as the connection of an unauthorized device, and the BPDU guard
feature places the interface into the ErrDisable state. The BPDU guard feature provides a secure
response to invalid configurations because you must manually put the interface back in service. For more
information, see the
When enabled on the switch, STP applies the BPDU guard feature to all Port Fast-enabled interfaces.
Note
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Catalyst 3550
switch
switch
Fast-enabled
Workstations
"Configuring BPDU Guard" section on page
Catalyst 6000
series switch
Catalyst 3550
switch
Port
ports
Workstations
Catalyst 3550 Multilayer Switch Software Configuration Guide
Understanding Advanced STP Features
Server
Port
Fast-enabled port
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