Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
What is the main purpose of BPDU Guard on a PortFast-enabled access port?
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
Distractor review
To elect the root bridge faster
BPDU Guard does not speed root election.
B
Best answer
To shut down an access port if a BPDU is received
Correct. That protects against unexpected switch connections on edge ports.
C
Distractor review
To convert all trunks to routed ports
BPDU Guard has nothing to do with routed ports.
D
Distractor review
To allow BPDUs only from trusted access points
That is not the function of BPDU Guard.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is selecting an answer that suggests BPDU Guard speeds up root bridge election or converts trunks to routed ports. Candidates may confuse BPDU Guard with other STP features or port configurations. BPDU Guard’s sole function is to shut down a PortFast-enabled access port if it receives a BPDU, signaling an unexpected switch connection. Misunderstanding this can lead to choosing incorrect options that describe unrelated behaviors, such as root bridge election acceleration or trusted BPDU filtering, which are not functions of BPDU Guard.
Technical deep dive
How to think about this question
Bridge Protocol Data Units (BPDUs) are special frames exchanged by switches to maintain Spanning Tree Protocol (STP), which prevents Layer 2 loops in a network. PortFast is a Cisco feature that immediately transitions a switch port into the forwarding state, bypassing the usual STP listening and learning states. This is typically enabled on access ports connected to end devices to speed up connectivity. However, if a BPDU is received on a PortFast-enabled port, it indicates that another switch might be connected, which could cause loops if not handled properly. BPDU Guard is a security feature designed to protect the network by shutting down a PortFast-enabled access port immediately upon receipt of a BPDU. This prevents accidental or malicious introduction of switches into the network topology on edge ports, which are expected to connect only to end devices. By disabling the port, BPDU Guard helps maintain STP stability and prevents potential Layer 2 loops that could disrupt network operations. A common exam trap is misunderstanding BPDU Guard’s role as a mechanism to speed up root bridge election or to manage trunk ports. BPDU Guard does not influence root bridge election timing nor does it convert ports to routed interfaces. Instead, it strictly protects PortFast ports by shutting them down if unexpected BPDUs arrive. In practical networks, enabling BPDU Guard on access ports ensures that any misconfiguration or unauthorized switch connection is quickly isolated, maintaining network integrity and avoiding broadcast storms caused by loops.
KKey Concepts to Remember
- BPDU Guard immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections.
- PortFast allows access ports to bypass STP listening and learning states, enabling faster transition to forwarding state for end devices.
- Receiving a BPDU on a PortFast port indicates a potential switch connection, which BPDU Guard treats as a network topology risk.
- BPDU Guard does not affect root bridge election speed or STP path cost calculations; it only protects edge ports from loops.
- Access ports with BPDU Guard enabled are placed into an error-disabled state when a BPDU is detected, requiring manual or automatic recovery.
- BPDU Guard is not related to converting trunk ports to routed ports or managing trusted access points for BPDUs.
- Enabling BPDU Guard on access ports enhances network stability by preventing accidental bridging loops from unauthorized devices.
- PortFast and BPDU Guard are complementary features designed to optimize edge port behavior while maintaining STP loop protection.
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 immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections.
What is the correct answer to this question?
The correct answer is: To shut down an access port if a BPDU is received — BPDU Guard helps prevent accidental loops by shutting down a PortFast port if it receives a BPDU.
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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