CCNA Switching and Network Access Practice Question
A switch port connected to a user PC should be placed in VLAN 20 and must not negotiate trunking. Which configuration is the most appropriate?
⚠ Common exam trap
Avoid assuming 'auto' mode is always safe; it can lead to unintended trunking.
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
✓
switchport mode access switchport access vlan 20
The most appropriate configuration is to force the interface into access mode and assign it to VLAN 20. In practical terms, a normal user-facing switch port is supposed to carry one VLAN only. There is no reason to rely on dynamic trunk negotiation for a desktop or laptop connection. Explicit access-port configuration is cleaner, more predictable, and safer. This is a common switching best-practice question. The wrong answers usually leave room for unwanted trunking behavior or move the interface into a completely different role. The right answer combines the correct port role with the correct VLAN membership.
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 mode access switchport access vlan 20
Why this is correct
This is the correct configuration for a host port. `switchport mode access` unconditionally sets the interface as a nontrunking Layer 2 access port, disabling Dynamic Trunking Protocol (DTP) and preventing the port from becoming a trunk. The `switchport access vlan 20` command then statically assigns the port to VLAN 20, so the connected PC’s untagged frames are carried in that VLAN, exactly matching the requirement.
- ✗
switchport mode trunk switchport trunk native vlan 20
Why it's wrong here
`switchport mode trunk` forces the port to operate in trunking mode, which is designed to carry tagged frames for multiple VLANs between switches, not to serve a single end device. The `switchport trunk native vlan 20` command only specifies which VLAN is used for untagged frames on that trunk; it does not make the port an access port in VLAN 20. A user PC would normally send untagged frames, but a trunk port expects 802.1Q tags except for the native VLAN, and enabling trunking on a host port is inappropriate and unnecessary.
When this WOULD be correct
This option would be correct in a scenario where the question specifies that the switch port is intended to connect to another switch or a device that requires trunking, and the native VLAN needs to be set to 20 for proper communication between VLANs.
- ✗
switchport mode dynamic desirable switchport trunk allowed vlan 20
Why it's wrong here
The `switchport mode dynamic desirable` command enables DTP and actively attempts to negotiate trunking with the connected device. Even though `switchport trunk allowed vlan 20` restricts the VLANs permitted on the trunk, the port can still become a trunk if the PC's NIC or an intermediate switch responds to DTP, which defeats the requirement for a static access port. Moreover, an access port in VLAN 20 cannot be configured using trunk allowed vlan commands, and this configuration leaves the port's final mode dependent on negotiation rather than explicitly placing the PC in VLAN 20.
When this WOULD be correct
In a different question setup where a switch port needs to connect to another switch and allow multiple VLANs, configuring the port as a trunk with 'switchport mode trunk' and specifying 'switchport trunk native vlan 20' would be appropriate to manage VLAN traffic effectively.
- ✗
no switchport ip address 192.168.20.1 255.255.255.0
Why it's wrong here
The `no switchport` command on supported Cisco switches converts the physical interface into a Layer 3 routed port, removing its Layer 2 switching capability entirely. Assigning an IP address with `ip address 192.168.20.1 255.255.255.0` then makes the port act like a router interface, not a switchport. A user PC connected to this port would not belong to any VLAN, and the switch would attempt to route traffic instead of bridging it in VLAN 20, so this configuration is incorrect for the stated requirement.
When this WOULD be correct
This option would be correct in a scenario where the question asks for the configuration of a router interface that needs to be assigned an IP address in VLAN 20 for inter-VLAN routing. In that case, the interface would not be a switchport but rather a routed interface.
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 mode access switchport access vlan 20Correct answer▾
Why this is correct
This is the correct configuration for a host port. `switchport mode access` unconditionally sets the interface as a nontrunking Layer 2 access port, disabling Dynamic Trunking Protocol (DTP) and preventing the port from becoming a trunk. The `switchport access vlan 20` command then statically assigns the port to VLAN 20, so the connected PC’s untagged frames are carried in that VLAN, exactly matching the requirement.
✗switchport mode trunk switchport trunk native vlan 20Wrong answer — click to see why▾
Why this is wrong here
This configuration makes the port a trunk port, which is used to carry multiple VLANs between switches, not for a single user PC. The 'switchport trunk native vlan 20' command sets the native VLAN for untagged traffic on the trunk, but the port still actively negotiates trunking via DTP, violating the requirement to not negotiate trunking.
★ When this WOULD be the correct answer
This option would be correct in a scenario where the question specifies that the switch port is intended to connect to another switch or a device that requires trunking, and the native VLAN needs to be set to 20 for proper communication between VLANs.
Why candidates choose this
A student might confuse 'native VLAN' with 'access VLAN' and think that setting the native VLAN to 20 on a trunk port achieves the same result as assigning VLAN 20 to an access port. They may also overlook that trunk ports are designed for inter-switch links, not end-user connections.
✗switchport mode dynamic desirable switchport trunk allowed vlan 20Wrong answer — click to see why▾
Why this is wrong here
The 'switchport mode dynamic desirable' command actively attempts to form a trunk with the connected device via DTP, which contradicts the requirement to not negotiate trunking. Additionally, 'switchport trunk allowed vlan 20' only restricts which VLANs are allowed on the trunk, but the port is still in trunking mode, not an access port.
★ When this WOULD be the correct answer
In a different question setup where a switch port needs to connect to another switch and allow multiple VLANs, configuring the port as a trunk with 'switchport mode trunk' and specifying 'switchport trunk native vlan 20' would be appropriate to manage VLAN traffic effectively.
Why candidates choose this
Students may think that 'dynamic desirable' is a safe mode that only becomes a trunk if the other side agrees, but it still initiates DTP negotiation. They might also incorrectly assume that 'trunk allowed vlan 20' limits the port to a single VLAN, similar to an access port.
✗no switchport ip address 192.168.20.1 255.255.255.0Wrong answer — click to see why▾
Why this is wrong here
The 'no switchport' command converts the Layer 2 switch port into a Layer 3 routed interface, which cannot be assigned to a VLAN. This configuration is used for routing between VLANs or connecting to routers, not for connecting a user PC to a specific VLAN.
★ When this WOULD be the correct answer
This option would be correct in a scenario where the question asks for the configuration of a router interface that needs to be assigned an IP address in VLAN 20 for inter-VLAN routing. In that case, the interface would not be a switchport but rather a routed interface.
Why candidates choose this
A student might think that assigning an IP address to the port is necessary for the PC to communicate, but on a Layer 2 switch, VLAN membership is handled at Layer 2, not by IP addressing. They may also confuse this with configuring a switch virtual interface (SVI) for VLAN 20, which is done on a different interface.
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?”
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Related to this question
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
VLAN
A VLAN (Virtual Local Area Network) is a logical grouping of network devices that behave as if they are on the same physical network segment, regardless of their actual physical location.
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.