CCNA Switching and Network Access Practice Question

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 voice VLAN is configured using the 'switchport mode trunk' command.

  Why it's wrong here

  The command 'switchport mode trunk' configures a port to carry multiple VLANs between switches, but it does not assign a voice VLAN. Voice VLAN is applied to an access port using 'switchport voice vlan', which allows a phone to tag its traffic while connected to a port that is otherwise an access port. Therefore, the statement confuses trunk configuration with the voice VLAN feature.

• ✓

  When a voice VLAN is configured, the switch port operates in two VLANs: one for data and one for voice traffic.

  Why this is correct

  With a voice VLAN configured, a single physical switchport simultaneously carries data and voice traffic by operating as an access port for the data VLAN and accepting tagged frames on the voice VLAN. The switch sets the port to 'switchport mode access' with 'switchport access vlan' for data and 'switchport voice vlan' for voice, so the port effectively bridges two separate VLANs. This is why a PC connected through an IP phone still gets an untagged data VLAN assignment while the phone's traffic is tagged with the voice VLAN ID.

• ✗

  The voice VLAN must be the same as the native VLAN on the trunk link.

  Why it's wrong here

  The native VLAN on a trunk is the VLAN that carries untagged frames, often VLAN 1 by default, and is a trunk-specific concept. The voice VLAN, by contrast, is a separate VLAN assigned to voice traffic on an access port and has no inherent relationship to the native VLAN. There is no requirement for them to match, and in practice they are usually distinct to maintain traffic separation.

• ✓

  The IP phone uses CDP or LLDP to learn the voice VLAN ID from the switch.

  Why this is correct

  Cisco IP phones use CDP (Cisco Discovery Protocol) and can also use LLDP-MED to discover the voice VLAN ID configured on the access port. After receiving this information, the phone tags its VoIP frames with the voice VLAN ID while leaving the connected PC's traffic untagged on the data VLAN. This automatic discovery allows phones to be deployed without manual configuration and ensures proper LAN segmentation for voice traffic.

• ✗

  The data VLAN and voice VLAN must be in the same IP subnet.

  Why it's wrong here

  Data and voice VLANs are intentionally separate Layer 2 broadcast domains, and they are typically assigned different IP subnets to facilitate QoS marking, security policy, and traffic management. There is no technical requirement that they share a subnet; in fact, placing them in the same subnet would defeat the purpose of using VLANs for traffic segregation. Therefore, the statement is incorrect because VLANs are designed to isolate traffic at Layer 2, and IP subnets are usually aligned with that separation.

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.

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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