The correct command is `switchport access vlan 30`, which directly assigns VLAN 30 to an interface already placed in access mode. This command works because an access port carries traffic for only one VLAN, so the switch must know exactly which VLAN to associate with the endpoint device connected to that port. On the CCNA 200-301 v2 exam, this tests your ability to distinguish between interface configuration modes: `switchport mode access` sets the port’s role, while `switchport access vlan` defines the VLAN membership for that role. A common trap is confusing this with `switchport trunk native vlan` or forgetting to first set the port to access mode, which leaves the interface in dynamic desirable mode and can cause unexpected trunking. Remember the memory tip: “Mode first, VLAN second” — you must lock the door (access mode) before you assign the room number (VLAN 30).
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. A key principle to apply: an access port on a Cisco switch carries traffic for only one VLAN and does not tag frames externally.. 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.
A switch interface connects to a user PC and should belong only to VLAN 30. Which command assigns that VLAN after the interface is in access mode?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
switchport access vlan 30
After an interface is placed into access mode, the command used to assign its VLAN is `switchport access vlan 30`. In plain language, this tells the switch which VLAN the endpoint traffic on that access port belongs to. Access mode defines the role of the interface, and the access VLAN command defines the specific VLAN membership for that role.
This distinction matters because some commands change the port’s behavior while others set the VLAN it uses. The correct answer is the one that directly assigns VLAN 30 to the access port rather than modifying a trunk or a native VLAN setting.
Key principle: An access port on a Cisco switch carries traffic for only one VLAN and does not tag frames externally.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
switchport access vlan 30
Why this is correct
This is correct because it assigns VLAN 30 to the access port.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
An access port on a Cisco switch carries traffic for only one VLAN and does not tag frames externally.
✗
switchport trunk allowed vlan 30
Why it's wrong here
This is wrong because it is a trunk-related command, not the normal access-port VLAN assignment.
When this WOULD be correct
In a scenario where the question asks how to configure a trunk port to allow only VLAN 30 traffic while excluding other VLANs, this command would be appropriate. For example, if the question specifies that the interface is in trunk mode and requires VLAN filtering, this command would be correct.
✗
encapsulation dot1Q 30
Why it's wrong here
This is wrong because 802.1Q encapsulation is not configured this way on a standard access switchport.
When this WOULD be correct
In a different exam scenario where the question asks about configuring a trunk interface to support multiple VLANs, 'encapsulation dot1Q 30' would be correct if the question specified that the trunk should allow VLAN 30 using 802.1Q encapsulation.
✗
ip helper-address 30
Why it's wrong here
This is wrong because DHCP relay is unrelated to assigning an access VLAN.
When this WOULD be correct
In a question asking for the configuration of a router to enable DHCP relay for clients on VLAN 30, where the router needs to forward requests to a DHCP server with the address '30', this command would be appropriate.
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.
✓switchport access vlan 30Correct answer▾
Why this is correct
This is correct because it assigns VLAN 30 to the access port.
✗switchport trunk allowed vlan 30Wrong answer — click to see why▾
Why this is wrong here
The command 'switchport trunk allowed vlan 30' is used on trunk ports to specify which VLANs are allowed to traverse the trunk link. It does not assign a VLAN to an access port; instead, it filters VLANs on a trunk, which is not appropriate for a port connected to a single PC.
★ When this WOULD be the correct answer
In a scenario where the question asks how to configure a trunk port to allow only VLAN 30 traffic while excluding other VLANs, this command would be appropriate. For example, if the question specifies that the interface is in trunk mode and requires VLAN filtering, this command would be correct.
Why candidates choose this
A student might confuse the concept of allowing VLANs on a trunk with assigning a VLAN to an access port, especially if they are familiar with trunk configuration but not clear on the distinction between access and trunk modes.
✗encapsulation dot1Q 30Wrong answer — click to see why▾
Why this is wrong here
The command 'encapsulation dot1Q 30' is used on a router subinterface to enable 802.1Q trunking and specify the VLAN for that subinterface. It is not a valid command on a switch access port, and switch ports do not use encapsulation commands for VLAN assignment.
★ When this WOULD be the correct answer
In a different exam scenario where the question asks about configuring a trunk interface to support multiple VLANs, 'encapsulation dot1Q 30' would be correct if the question specified that the trunk should allow VLAN 30 using 802.1Q encapsulation.
Why candidates choose this
Students might associate 'dot1Q' with VLANs and think that specifying a VLAN number with this command would assign the VLAN to the port, not realizing that encapsulation is for trunking and not for access port configuration.
✗ip helper-address 30Wrong answer — click to see why▾
Why this is wrong here
The command 'ip helper-address 30' is used to configure DHCP relay on a router or Layer 3 switch interface, forwarding DHCP broadcasts to a DHCP server. It has nothing to do with VLAN assignment on a switch port.
★ When this WOULD be the correct answer
In a question asking for the configuration of a router to enable DHCP relay for clients on VLAN 30, where the router needs to forward requests to a DHCP server with the address '30', this command would be appropriate.
Why candidates choose this
A student might mistakenly think that 'helper-address' is related to VLAN assignment because both involve IP addressing and VLANs, but this command serves a completely different purpose in DHCP relay.
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
Be careful not to confuse commands for trunk ports with those for access ports. Ensure you understand the difference between setting a port mode and assigning a VLAN.
Trap categories for this question
Command / output trap
This is wrong because it is a trunk-related command, not the normal access-port VLAN assignment.
Detailed technical explanation
How to think about this question
VLANs (Virtual Local Area Networks) segment a physical switch into multiple logical networks, isolating traffic for security and performance. An access port on a switch connects end devices like PCs and assigns them to a single VLAN, ensuring their traffic is tagged internally with that VLAN ID. The command `switchport mode access` configures the interface as an access port, which means it carries traffic for only one VLAN without tagging frames externally.
To assign a specific VLAN to an access port, the command `switchport access vlan <vlan-id>` is used. This command explicitly sets the VLAN membership for the port after it is in access mode. For example, `switchport access vlan 30` binds the port to VLAN 30, so all traffic from the connected device is associated with VLAN 30. This is essential for proper VLAN segmentation and traffic forwarding within the switch.
A common exam trap is confusing access port VLAN assignment with trunk port commands or unrelated features. Commands like `switchport trunk allowed vlan` apply only to trunk ports that carry multiple VLANs, not access ports. Similarly, `encapsulation dot1Q` is used on router subinterfaces or trunk ports, not on access ports. Understanding the difference between access and trunk modes and their respective commands is critical to avoid mistakes and correctly configure VLAN membership on Cisco switches.
KKey Concepts to Remember
An access port on a Cisco switch carries traffic for only one VLAN and does not tag frames externally.
The command `switchport mode access` configures an interface to operate as an access port.
The command `switchport access vlan <vlan-id>` assigns a specific VLAN to an access port after it is in access mode.
Trunk ports carry multiple VLANs and use commands like `switchport trunk allowed vlan` to control VLAN membership.
The `encapsulation dot1Q` command configures 802.1Q tagging on router subinterfaces or trunk ports, not on access ports.
Assigning the correct VLAN to an access port ensures proper traffic segmentation and forwarding within the switch.
Misapplying trunk or encapsulation commands on access ports leads to configuration errors and connectivity issues.
Understanding the difference between access and trunk port configurations is essential for VLAN management in Cisco networks.
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
An access port on a Cisco switch carries traffic for only one VLAN and does not tag frames externally.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review an access port on a Cisco switch carries traffic for only one VLAN and does not tag frames externally., then practise related 200-301 questions on the same topic to reinforce the concept.
Switching and Network Access — This question tests Switching and Network Access — An access port on a Cisco switch carries traffic for only one VLAN and does not tag frames externally..
What is the correct answer to this question?
The correct answer is: switchport access vlan 30 — After an interface is placed into access mode, the command used to assign its VLAN is `switchport access vlan 30`. In plain language, this tells the switch which VLAN the endpoint traffic on that access port belongs to. Access mode defines the role of the interface, and the access VLAN command defines the specific VLAN membership for that role.
This distinction matters because some commands change the port’s behavior while others set the VLAN it uses. The correct answer is the one that directly assigns VLAN 30 to the access port rather than modifying a trunk or a native VLAN setting.
What should I do if I get this 200-301 question wrong?
Review an access port on a Cisco switch carries traffic for only one VLAN and does not tag frames externally., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
An access port on a Cisco switch carries traffic for only one VLAN and does not tag frames externally.
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