Question:
When an interface is configured with PortFast BPDU guard, how does the interface respond when it receives a BPDU?
- It continues operating normally.
- It goes into a down/down state.
- It becomes the root bridge for the configured VLAN.
- It goes into an errdisable state.
Explanation: PortFast BPDU guard prevents loops by moving a nontrunking port into an errdisable state when a BPDU is received on that port. When you enable BPDU guard on the switch, spanning tree shuts down PortFast-configured interfaces that receive BPDUs instead of putting them into the spanning tree blocking state.
In a valid configuration, PortFast-configured interfaces do not receive BPDUs (because PortFast should only be configured on interfaces which are connected to hosts). If a PortFast-configured interface receives a BPDU, an invalid configuration exists. BPDU guard provides a secure response to invalid configurations because the administrator must manually put the interface back in service.
Exam with this question: CCNA v3.0 (200-125) Study Guide – Exam Dumps
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