350-401 Question 135
Single answerYou are configuring a campus network with Rapid Spanning Tree Protocol (RSTP) to ensure fast convergence while maintaining a loop-free topology. To prevent misconfigurations caused by unauthorized devices sending Bridge Protocol Data Units (BPDUs) on access ports, which feature should you enable on these ports?
- A
Root Guard
- B
BPDU Guard
- C
PortFast
- D
Loop Guard
Show answer and explanation
Correct answer: B
Explanation
BPDU Guard is the appropriate feature to secure access ports against unauthorized devices sending BPDUs. It ensures that if a BPDU is received on a port where BPDU Guard is enabled, the port is immediately shut down to protect the network's spanning tree topology. This is particularly useful in conjunction with PortFast on access ports.
- A. Incorrect.
Root Guard is used to protect the root bridge by preventing other switches from becoming the root through superior BPDUs, but it does not prevent BPDUs on access ports from unauthorized devices.
- B. Correct.
BPDU Guard disables a port if a BPDU is received, which is ideal for access ports where no BPDUs should ever be sent by end devices, ensuring network stability.
- C. Incorrect.
PortFast is used to transition a port to the forwarding state immediately, but it does not protect against unauthorized BPDUs.
- D. Incorrect.
Loop Guard prevents alternate or root ports from transitioning to the forwarding state due to the absence of BPDUs, but it does not address the issue of unauthorized BPDUs on access ports.