Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A Layer 2 switch port connected to an end host should move to forwarding quickly but also shut down if a BPDU is received. Which pair of features best supports that design?
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 and BPDU Guard
This is correct because PortFast speeds edge-port forwarding and BPDU Guard disables the port if a BPDU is received.
B
Distractor review
Root Guard and UDLD
This is wrong because those features do not match the specific edge-port requirement described.
C
Distractor review
Loop Guard and native VLAN
This is wrong because those settings do not provide the required behavior.
D
Distractor review
Port security and EtherChannel
This is wrong because EtherChannel is unrelated to the STP edge-port requirement.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is selecting Root Guard or Loop Guard instead of BPDU Guard for protecting edge ports. Root Guard prevents a port from becoming a root port but does not shut down the port on BPDU receipt. Loop Guard protects against unidirectional link failures on blocked ports but does not disable ports receiving BPDUs. Another trap is assuming PortFast alone is sufficient; PortFast speeds up forwarding but does not protect the port from receiving BPDUs, which could cause loops or topology changes. The correct combination is PortFast for fast forwarding and BPDU Guard for safety.
Technical deep dive
How to think about this question
Spanning Tree Protocol (STP) is essential in Layer 2 networks to prevent loops by selectively blocking redundant paths. Edge ports, which connect directly to end devices rather than other switches, benefit from PortFast. PortFast immediately transitions the port to the forwarding state, bypassing the usual STP listening and learning states, thus reducing connection delay for end hosts. However, if a BPDU (Bridge Protocol Data Unit) is received on a PortFast-enabled port, it indicates a potential switch connection or loop, which is unsafe for an edge port. BPDU Guard complements PortFast by protecting the network from misconfigurations or malicious devices. When BPDU Guard is enabled on a PortFast port, the switch automatically disables (err-disables) the port if it receives any BPDU frames. This behavior prevents potential loops or STP topology changes caused by unexpected switches connected to edge ports. Together, PortFast and BPDU Guard ensure fast connectivity for legitimate end devices while maintaining network stability and security. A common exam trap is confusing BPDU Guard with Root Guard or Loop Guard. Root Guard protects the root bridge placement and Loop Guard prevents loops on blocked ports but neither disables the port upon receiving BPDUs on edge ports. PortFast alone speeds up forwarding but does not protect against BPDUs. The practical network implication is that enabling both PortFast and BPDU Guard on access ports connected to end hosts is a best practice to ensure fast and safe Layer 2 connectivity, which is exactly what the CCNA exam tests.
KKey Concepts to Remember
- PortFast immediately transitions a Layer 2 switch port to forwarding state to reduce connection delay for end hosts.
- BPDU Guard disables a PortFast-enabled port if any BPDU frames are received, preventing potential network loops.
- A Layer 2 switch port connected to an end host should use PortFast to speed up STP convergence on that port.
- BPDU Guard protects edge ports by err-disabling ports that receive unexpected spanning-tree BPDUs.
- Root Guard prevents a switch port from becoming a root port but does not disable the port upon BPDU receipt.
- Loop Guard prevents STP loops on blocked ports but does not affect edge port behavior with BPDUs.
- EtherChannel bundles multiple links for redundancy and bandwidth but does not influence edge port STP behavior.
- Native VLAN configuration does not provide protection against BPDUs or speed up port forwarding states.
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 Layer 2 switch port to forwarding state to reduce connection delay for end hosts.
What is the correct answer to this question?
The correct answer is: PortFast and BPDU Guard — PortFast and BPDU Guard are the right pair. In plain language, PortFast makes an edge port usable quickly for a real end device, while BPDU Guard protects that same port by shutting it down if spanning-tree control traffic appears unexpectedly. This is a classic access-layer design. PortFast improves usability, and BPDU Guard improves safety. The best answer combines both functions.
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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