- A
The native VLAN on a trunk port sends frames with an 802.1Q tag containing VLAN ID 1.
Why wrong: Native VLAN frames are sent untagged; no 802.1Q tag is added unless the native VLAN is explicitly changed and the port is configured to tag it.
- B
802.1Q trunking adds a 4-byte tag that includes a 12-bit VLAN ID field, increasing the maximum frame size.
The 802.1Q tag is 4 bytes, consisting of TPID and TCI, where the TCI contains a 12-bit VLAN ID.
- C
A router-on-a-stick configuration uses subinterfaces, each mapped to a VLAN with 802.1Q encapsulation and an IP address in a unique subnet.
Router-on-a-stick employs one physical interface divided into logical subinterfaces, each configured with 'encapsulation dot1q <vlan>' and an IP address to route between VLANs.
- D
A trunk port can only forward traffic for one VLAN at a time.
Why wrong: Trunks carry traffic for multiple VLANs simultaneously by tagging frames with VLAN identifiers.
- E
The native VLAN on a trunk cannot be changed from VLAN 1.
Why wrong: The native VLAN is configurable on a per‑trunk basis using the 'switchport trunk native vlan' command.
CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 TWO statements accurately describe 802.1Q trunking and inter-VLAN routing on Cisco switches?
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 adds a 4-byte tag that includes a 12-bit VLAN ID field, increasing the maximum frame size.
Option B is correct because 802.1Q trunking inserts a 4-byte tag into the Ethernet frame, which includes a 12-bit VLAN ID field (supporting up to 4094 VLANs). This tag increases the maximum frame size from 1518 bytes to 1522 bytes, which is a key characteristic of 802.1Q encapsulation.
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.
- ✗
The native VLAN on a trunk port sends frames with an 802.1Q tag containing VLAN ID 1.
Why it's wrong here
Native VLAN frames are sent untagged; no 802.1Q tag is added unless the native VLAN is explicitly changed and the port is configured to tag it.
- ✓
802.1Q trunking adds a 4-byte tag that includes a 12-bit VLAN ID field, increasing the maximum frame size.
Why this is correct
The 802.1Q tag is 4 bytes, consisting of TPID and TCI, where the TCI contains a 12-bit VLAN ID.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
A router-on-a-stick configuration uses subinterfaces, each mapped to a VLAN with 802.1Q encapsulation and an IP address in a unique subnet.
Why this is correct
Router-on-a-stick employs one physical interface divided into logical subinterfaces, each configured with 'encapsulation dot1q <vlan>' and an IP address to route between VLANs.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
A trunk port can only forward traffic for one VLAN at a time.
Why it's wrong here
Trunks carry traffic for multiple VLANs simultaneously by tagging frames with VLAN identifiers.
- ✗
The native VLAN on a trunk cannot be changed from VLAN 1.
Why it's wrong here
The native VLAN is configurable on a per‑trunk basis using the 'switchport trunk native vlan' command.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓802.1Q trunking adds a 4-byte tag that includes a 12-bit VLAN ID field, increasing the maximum frame size.Correct answer▾
Why this is correct
The 802.1Q tag is 4 bytes, consisting of TPID and TCI, where the TCI contains a 12-bit VLAN ID.
✗The native VLAN on a trunk port sends frames with an 802.1Q tag containing VLAN ID 1.Wrong answer — click to see why▾
Why this is wrong here
By default, frames belonging to the native VLAN (VLAN 1) traverse a trunk link without an 802.1Q tag.
✗A trunk port can only forward traffic for one VLAN at a time.Wrong answer — click to see why▾
Why this is wrong here
Trunk ports differentiate frames from multiple VLANs using VLAN tags, permitting concurrent forwarding for all allowed VLANs.
✗The native VLAN on a trunk cannot be changed from VLAN 1.Wrong answer — click to see why▾
Why this is wrong here
Cisco switches allow administrators to assign any active VLAN as the native VLAN for a trunk port.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that the native VLAN is always VLAN 1 and that it is tagged, when in fact the native VLAN is untagged and can be changed to any VLAN number.
Trap categories for this question
Command / output trap
The native VLAN is configurable on a per‑trunk basis using the 'switchport trunk native vlan' command.
Detailed technical explanation
How to think about this question
The 802.1Q tag uses a 4-byte field that includes a 2-byte TPID (0x8100) and a 2-byte TCI containing a 3-bit priority code point (PCP), a 1-bit drop eligible indicator (DEI), and a 12-bit VLAN ID (VID). In a router-on-a-stick setup, the router's subinterfaces use 802.1Q encapsulation to tag frames for specific VLANs, allowing a single physical link to route between multiple VLANs. A real-world scenario is when an access switch trunking to a distribution switch must ensure the native VLAN matches on both ends to avoid VLAN mismatch errors.
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
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FAQ
Questions learners often ask
What does this 200-301 question test?
Switching and Network Access — This question tests Switching and Network Access — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 802.1Q trunking adds a 4-byte tag that includes a 12-bit VLAN ID field, increasing the maximum frame size. — Option B is correct because 802.1Q trunking inserts a 4-byte tag into the Ethernet frame, which includes a 12-bit VLAN ID field (supporting up to 4094 VLANs). This tag increases the maximum frame size from 1518 bytes to 1522 bytes, which is a key characteristic of 802.1Q encapsulation.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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