Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A switch should disable an edge port immediately if a BPDU is received on it. Which feature is intended for that specific behavior?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
BPDU Guard
This is correct because BPDU Guard disables the edge port when a BPDU is received.
B
Distractor review
Loop Guard
This is wrong because loop guard addresses different STP conditions.
C
Distractor review
Root Guard
This is wrong because root guard is intended to stop a port from becoming a root port under superior BPDU conditions.
D
Distractor review
UDLD
This is wrong because UDLD deals with unidirectional link detection rather than BPDU-based edge protection.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is confusing BPDU Guard with Root Guard or Loop Guard. Candidates may incorrectly select Root Guard because it also deals with BPDUs, but Root Guard only blocks ports from becoming root ports and does not disable the port immediately. Loop Guard protects against unidirectional link failures and does not shut down ports upon BPDU receipt. Another mistake is thinking UDLD handles BPDU protection; however, UDLD only detects unidirectional physical link failures and is unrelated to STP BPDU processing. Understanding that BPDU Guard uniquely disables edge ports upon BPDU detection is critical to avoid this trap.
Technical deep dive
How to think about this question
BPDU Guard is a Cisco Catalyst switch feature designed to protect the Spanning Tree Protocol (STP) topology by disabling ports configured as edge ports when they receive Bridge Protocol Data Units (BPDUs). Edge ports are typically connected to end devices like PCs or printers and are expected not to participate in STP. Receiving a BPDU on such a port indicates a potential misconfiguration or unauthorized switch connection, which could cause network loops or topology instability. When BPDU Guard is enabled on an edge port, the switch continuously monitors for incoming BPDUs. If a BPDU is detected, BPDU Guard immediately places the port into an err-disabled state, effectively shutting it down to prevent any possible STP topology disruption. This behavior differs from other STP protection features like Root Guard and Loop Guard, which address different STP issues such as preventing a port from becoming a root port or protecting against unidirectional link failures. A common exam trap is confusing BPDU Guard with Root Guard or Loop Guard. While Root Guard blocks ports that attempt to become root ports, and Loop Guard protects against indirect link failures, only BPDU Guard aggressively disables edge ports upon BPDU receipt. In practical networks, BPDU Guard is critical for securing access ports against rogue switches or accidental loops, ensuring stable STP operation and preventing broadcast storms.
KKey Concepts to Remember
- BPDU Guard disables an edge port immediately when it receives a BPDU to prevent accidental loops or rogue switch connections.
- Edge ports are configured as portfast ports that connect directly to end devices and should not receive BPDUs under normal operation.
- Root Guard prevents a port from becoming a root port by blocking superior BPDUs but does not disable the port upon BPDU receipt.
- Loop Guard protects against unidirectional link failures by preventing a port from transitioning to a forwarding state when BPDUs stop arriving.
- UDLD detects unidirectional links and does not interact with BPDU processing or STP edge port protection.
- BPDU Guard places the port into an err-disabled state, requiring manual or automatic recovery to re-enable the port.
- Enabling BPDU Guard on edge ports enhances network stability by quickly isolating misconfigured or malicious devices.
- BPDU Guard is the specific STP feature designed to shut down a port immediately upon receiving any BPDU on an edge port.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
BPDU Guard disables an edge port immediately when it receives a BPDU to prevent accidental loops or rogue switch connections.
What is the correct answer to this question?
The correct answer is: BPDU Guard — The feature is BPDU Guard. In plain language, the administrator is treating the port as an end-device-only edge interface and wants the switch to react aggressively if it ever sees spanning-tree control traffic there. BPDU Guard does exactly that: if a BPDU appears on a protected edge port, the switch places the interface into an err-disabled state to help prevent accidental loops or rogue switch connections. This is different from root guard and loop guard, which solve other spanning-tree control problems. BPDU Guard is the specific answer when the requirement is “if you ever hear a BPDU here, shut the port down quickly.”
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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