Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A switch port connected to an edge host immediately transitions to forwarding and then later goes err-disabled after a BPDU is received. Which feature combination most likely produced this 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
PortFast with BPDU Guard
This is correct because PortFast speeds forwarding and BPDU Guard disables the edge port if a BPDU appears.
B
Distractor review
NetFlow with SNMP traps
This is wrong because those are visibility technologies, not STP edge-port controls.
C
Distractor review
OSPF passive-interface with EUI-64
This is wrong because those features are unrelated to switchport STP behavior.
D
Distractor review
WPA3 with CAPWAP
This is wrong because those are wireless concepts, not wired edge-port protections.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is confusing PortFast with general STP behavior or assuming that BPDU Guard simply blocks BPDUs without disabling the port. Some candidates incorrectly think that receiving a BPDU on any port is normal or that PortFast alone protects the network from loops. The trap also includes mixing unrelated features like OSPF or wireless protocols, which do not affect STP port states. Understanding that BPDU Guard actively disables the port upon BPDU receipt is critical to avoid this mistake.
Technical deep dive
How to think about this question
PortFast is a Cisco Catalyst switch feature that immediately transitions a switch port into the forwarding state, bypassing the usual Spanning Tree Protocol (STP) listening and learning states. This behavior is designed for ports connected directly to end devices, such as workstations or servers, to reduce the delay in network connectivity during link initialization. BPDU Guard is a complementary STP feature that disables a PortFast-enabled port if it receives a Bridge Protocol Data Unit (BPDU). Since edge ports should not receive BPDUs, the presence of a BPDU indicates a potential network topology change or misconfiguration. BPDU Guard places the port into an err-disabled state to prevent possible loops or STP disruptions. The combination of PortFast and BPDU Guard is a common enterprise best practice to protect the network edge. PortFast accelerates host connectivity, while BPDU Guard prevents accidental or malicious introduction of switches or bridges on edge ports. The exam trap is confusing PortFast with other unrelated features or misunderstanding BPDU Guard’s role, which can lead to incorrect answers about STP behavior and edge port security.
KKey Concepts to Remember
- PortFast immediately transitions a switch port to forwarding state to speed up host connectivity by skipping STP listening and learning states.
- BPDU Guard disables a PortFast-enabled port by placing it in err-disabled state if any BPDU is received on that port.
- Edge ports configured with PortFast should never receive BPDUs under normal network operation.
- Receiving a BPDU on a PortFast-enabled port triggers BPDU Guard to protect the network from potential loops or misconfigurations.
- BPDU Guard helps maintain network stability by preventing unauthorized switches from connecting to edge ports.
- PortFast and BPDU Guard together form a security mechanism that balances fast host access with loop prevention.
- Switch ports connected to other switches should not use PortFast because they need to participate fully in STP.
- Err-disabled state caused by BPDU Guard requires manual or automatic recovery to restore port functionality.
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?
PortFast immediately transitions a switch port to forwarding state to speed up host connectivity by skipping STP listening and learning states.
What is the correct answer to this question?
The correct answer is: PortFast with BPDU Guard — The most likely combination is PortFast with BPDU Guard. In practical terms, PortFast explains why the port moved quickly into forwarding when the host connected. BPDU Guard explains why the same port later shut down after seeing a BPDU that should not normally appear on an edge port. This is a very common enterprise edge-port design pattern and a classic exam scenario.
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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