Question 1mediummulti select
Full question →mediummulti selectObjective-mapped
A switchport connected to an employee PC must allow the normal endpoint to connect but immediately err-disable the port if a switch is plugged in. Which two features should be configured on that 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
Best answer
spanning-tree bpduguard enable
BPDU Guard shuts down an access port that unexpectedly receives BPDUs from another switch.
B
Distractor review
switchport port-security maximum 1
This limits MAC addresses but does not specifically detect a switch uplink.
C
Best answer
spanning-tree portfast
BPDU Guard is typically paired with PortFast on end-host access ports.
D
Distractor review
storm-control broadcast level 5.00
Storm control limits traffic rates; it does not err-disable on switch attachment.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is selecting 'switchport port-security maximum 1' as a solution to prevent unauthorized switches. While port security limits MAC addresses, it does not detect BPDUs or immediately disable the port if a switch is connected. This can allow a switch to connect and cause Layer 2 loops. Another trap is confusing storm control with BPDU Guard; storm control only limits broadcast traffic rates and does not err-disable ports on BPDU reception. Candidates must understand that only BPDU Guard combined with PortFast provides the immediate err-disable protection for access ports against switch connections.
Technical deep dive
How to think about this question
Spanning Tree Protocol (STP) is designed to prevent Layer 2 loops in a switched network by blocking redundant paths. Normally, when a switchport comes up, STP places it in a listening and learning state before forwarding traffic, which can delay endpoint connectivity. PortFast is a Cisco enhancement that immediately transitions the port to the forwarding state, assuming the port connects to an end device, not another switch. This reduces connection delays for devices like PCs. BPDU Guard is a complementary feature that protects the network by err-disabling a PortFast-enabled port if it receives any BPDUs. Since BPDUs are only sent by switches or bridges, their presence on a PortFast port indicates an unauthorized or misconnected switch. Err-disabling the port prevents potential Layer 2 loops and topology instability. This combination is essential for security and stability on access ports connected to end devices. A common exam trap is confusing Port Security with BPDU Guard. While Port Security limits the number of MAC addresses on a port, it does not detect BPDUs or prevent switch connections effectively. Storm control limits broadcast traffic but does not err-disable ports on BPDU reception. Understanding the distinct roles of PortFast and BPDU Guard helps avoid misconfigurations and ensures proper protection of access ports in Cisco networks.
KKey Concepts to Remember
- Spanning-tree PortFast immediately transitions a switchport to the forwarding state, allowing end devices to connect without delay during STP convergence.
- BPDU Guard disables a port that receives Bridge Protocol Data Units (BPDUs) unexpectedly, protecting the network from potential loops caused by unauthorized switches.
- An access port configured with PortFast assumes it connects to an end device and not another switch, speeding up port activation.
- BPDU Guard works by err-disabling the port if any BPDU frames are detected, which indicates a switch or bridge is connected instead of a normal endpoint.
- Port security limiting MAC addresses does not detect switch connections because switches can forward multiple MAC addresses, so it cannot reliably prevent switch uplinks.
- Storm control limits broadcast traffic rates but does not err-disable ports upon detecting switch connections or BPDUs.
- Combining PortFast and BPDU Guard on access ports ensures fast connectivity for legitimate endpoints and immediate shutdown if a switch is connected, preventing STP topology issues.
- Switches use BPDUs to exchange spanning-tree information; receiving BPDUs on an access port configured for end devices is a sign of misconfiguration or unauthorized device.
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?
Spanning-tree PortFast immediately transitions a switchport to the forwarding state, allowing end devices to connect without delay during STP convergence.
What is the correct answer to this question?
The correct answer is: spanning-tree bpduguard enable — For edge access ports, PortFast brings the port up quickly for end devices, and BPDU Guard protects against someone connecting a switch by err-disabling the interface when BPDUs arrive.
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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