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Open the full VLAN trunking answer →Question 1,371 of 1,819
Quick Answer
The answer is to manually set the trunk mode and avoid DTP negotiation errors, as this directly addresses security risks and configuration mismatches on 802.1Q trunk links. This best practice stems from the fact that Dynamic Trunking Protocol (DTP) can be exploited by an attacker to negotiate a trunk, potentially granting unauthorized VLAN access, while manually configuring trunk mode eliminates that vulnerability. On the CCNA 200-301 v2 exam, this concept tests your understanding of Layer 2 switch security and the operational behavior of 802.1Q trunking, often appearing in questions that contrast dynamic negotiation with static configuration. A common trap is assuming DTP is harmless or that the native VLAN should remain as VLAN 1 for simplicity, but the exam emphasizes that the native VLAN must match on both ends and should be changed to a non-default, unused VLAN to prevent misdirection and VLAN hopping. Remember the mnemonic “No DTP, No VLAN 1” to lock in the two core best practices: disable DTP by setting trunk mode manually, and never use VLAN 1 as the native VLAN.
CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Which four of the following correctly describe characteristics or best practices for VLAN trunking and Layer 2 switch configuration? (Choose four.)
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
802.1Q trunking uses a native VLAN that carries untagged traffic; both ends of the trunk must agree on the native VLAN.
802.1Q trunking defines a native VLAN that carries untagged traffic; both ends must agree on the native VLAN to prevent misdirection and security issues. DTP can negotiate trunking between Cisco switches when ports are set to dynamic desirable or trunk mode, allowing automatic trunk establishment. VTP in transparent mode forwards VTP advertisements to other switches but does not synchronize its VLAN database, making it safe for maintaining local VLAN control. Manually setting trunk mode is a best practice to avoid DTP negotiation errors and security risks, as DTP can be exploited. Option 3 is incorrect because using VLAN 1 for user traffic is a security vulnerability; it is recommended to change the native VLAN and prune VLAN 1. Option 4 is incorrect because an access port belongs to only one VLAN; VLAN pruning is used on trunk links to restrict VLAN traffic, not to allow an access port to carry multiple VLANs.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that VLAN 1 is a best practice for user traffic, when in fact it is a well-known security vulnerability and should be changed or pruned.
Detailed technical explanation
How to think about this question
802.1Q inserts a 4-byte tag into the Ethernet frame, recalculating the FCS; the native VLAN is the only VLAN that remains untagged on a trunk, allowing interoperability with devices that do not understand tagging. DTP uses Cisco-proprietary frames (DTP frames) to negotiate trunking; setting both ends to 'dynamic desirable' or 'trunk' results in a trunk, but 'dynamic auto' requires the other side to initiate. VTP transparent mode forwards VTP advertisements out trunk ports but does not apply updates to its own VLAN database, making it useful for isolating VLAN changes in a network segment.
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.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 802.1Q trunking uses a native VLAN that carries untagged traffic; both ends of the trunk must agree on the native VLAN. — 802.1Q trunking defines a native VLAN that carries untagged traffic; both ends must agree on the native VLAN to prevent misdirection and security issues. DTP can negotiate trunking between Cisco switches when ports are set to dynamic desirable or trunk mode, allowing automatic trunk establishment. VTP in transparent mode forwards VTP advertisements to other switches but does not synchronize its VLAN database, making it safe for maintaining local VLAN control. Manually setting trunk mode is a best practice to avoid DTP negotiation errors and security risks, as DTP can be exploited. Option 3 is incorrect because using VLAN 1 for user traffic is a security vulnerability; it is recommended to change the native VLAN and prune VLAN 1. Option 4 is incorrect because an access port belongs to only one VLAN; VLAN pruning is used on trunk links to restrict VLAN traffic, not to allow an access port to carry multiple VLANs.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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