The correct answer is to remove the spanning-tree portfast command from the interface. This is because enabling Spanning-Tree PortFast on a trunk port forces the port into the forwarding state immediately, bypassing the normal listening and learning phases of spanning-tree convergence. When a trunk port connected to a server has PortFast active, any loop introduced—such as from a misconfigured NIC team or an accidental downstream switch connection—will not be detected in time, causing a temporary bridging loop that results in intermittent network drops. On the CompTIA Project+ PK0-005 exam, this scenario tests your understanding that PortFast is intended only for access ports connecting to end devices, not for trunk ports that may carry multiple VLANs or connect to other switches. A common trap is assuming PortFast speeds up all ports, but on trunks it creates instability. Remember the memory tip: “Trunks need time to think—PortFast is for endpoints, not links.”
PK0-005 Practice Question: Basics of IT Infrastructure and IT Project Management
This PK0-005 practice question tests your understanding of basics of it infrastructure and it project management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Refer to the exhibit.
Exhibit:
```
interface GigabitEthernet0/1
switchport mode trunk
switchport trunk allowed vlan 10,20,30
spanning-tree portfast
```
A network engineer configures a switch port as shown. After implementation, the connected server is experiencing intermittent network drops. Which configuration change should the project team recommend to resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Remove the spanning-tree portfast command from the interface
The intermittent network drops are caused by spanning-tree PortFast being enabled on a trunk port connected to a server. PortFast immediately transitions the port to the forwarding state, bypassing the normal spanning-tree listening and learning states. If a loop is introduced (e.g., via a misconfigured NIC team or a downstream switch), the switch will not detect it in time, leading to a temporary bridging loop and packet loss. Removing PortFast forces the port to go through the full spanning-tree convergence process, preventing loops and stabilizing the connection.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Add additional VLANs to the allowed list
Why it's wrong here
Adding VLANs does not fix the portfast misconfiguration.
✗
Disable trunk encapsulation on the interface
Why it's wrong here
Trunk encapsulation is typically auto-negotiated; disabling it would break the link.
✓
Remove the spanning-tree portfast command from the interface
Why this is correct
Portfast is designed for access ports; on trunk ports it can cause bridging loops and drops.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change the interface mode to access
Why it's wrong here
Changing to access mode would remove VLAN trunking, likely breaking connectivity.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that PortFast is harmless on any port, but the trap here is that PortFast should never be used on trunk ports or ports connected to devices that could participate in bridging, as it bypasses STP loop prevention and causes intermittent drops during topology changes.
Detailed technical explanation
How to think about this question
Spanning Tree Protocol (STP) uses four port states: blocking, listening, learning, and forwarding. PortFast is designed for end-user devices (like PCs) that never create loops, but when applied to a trunk port connected to a server with NIC teaming or a virtual switch, it can cause temporary loops because the switch forwards frames before STP converges. The intermittent drops occur when a BPDU (Bridge Protocol Data Unit) is received on a PortFast-enabled port, triggering errdisable state or causing the switch to re-run STP, disrupting traffic.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Basics of IT Infrastructure and IT Project Management — This question tests Basics of IT Infrastructure and IT Project Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Remove the spanning-tree portfast command from the interface — The intermittent network drops are caused by spanning-tree PortFast being enabled on a trunk port connected to a server. PortFast immediately transitions the port to the forwarding state, bypassing the normal spanning-tree listening and learning states. If a loop is introduced (e.g., via a misconfigured NIC team or a downstream switch), the switch will not detect it in time, leading to a temporary bridging loop and packet loss. Removing PortFast forces the port to go through the full spanning-tree convergence process, preventing loops and stabilizing the connection.
What should I do if I get this PK0-005 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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