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.

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  VLAN: Encapsulates frames with a VLAN tag

  Why it's wrong here

  VLANs partition a physical switch into multiple logical broadcast domains, so frames within a VLAN are switched only to ports in that same VLAN. They do not encapsulate frames with a VLAN tag; that task belongs to 802.1Q trunking, which inserts a four-byte tag into the Ethernet frame to identify the VLAN. Confusing the two conflates the logical segmentation provided by VLANs with the tagging mechanism used to carry multiple VLANs over a single link, which is a trunking feature.

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  802.1Q trunking: Carries untagged traffic on a trunk

  Why it's wrong here

  802.1Q trunking is the protocol that adds a four-byte VLAN tag to Ethernet frames, allowing multiple VLANs to traverse a single trunk link. It does not carry untagged traffic; rather, the native VLAN is the exception that carries frames without a tag, typically for interoperability with devices that do not understand tagging. So the statement incorrectly describes the native VLAN's behavior as the protocol's primary function.

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  Native VLAN: Segments a switch into multiple broadcast domains

  Why it's wrong here

  The native VLAN is the VLAN that carries untagged frames on an 802.1Q trunk, typically defaulting to VLAN 1. It is a subset of trunking behavior, not a mechanism for segmenting broadcast domains; that segmentation is the general purpose of any VLAN. Saying it segments a switch into broadcast domains confuses the specific native VLAN's role with the broader concept of VLANs, which is a common misconception.

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  switchport mode trunk: Configures a trunk port

  Why this is correct

  The Cisco IOS command 'switchport mode trunk', executed in interface configuration mode, forcibly sets the access port to act as an 802.1Q trunk. This enables the port to carry frames for multiple VLANs, each tagged with its VLAN ID, and stops DTP negotiation to establish the trunk unconditionally. It is a common configuration when connecting switches or to a router, ensuring that VLAN traffic is not limited to a single VLAN like an access port.

• ✓

  show vlan brief: Lists VLAN assignments

  Why this is correct

  The privileged EXEC command 'show vlan brief' provides a concise table of all VLANs on the switch, listing their IDs, names, status, and the access ports assigned to each VLAN. It does not show trunk ports or tagging details, making it useful for verifying VLAN creation and port assignments after configuration. This command is often the first step in troubleshooting VLAN membership issues, as it offers a quick snapshot of the VLAN database.

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  inter-VLAN routing: Enables communication between VLANs typically using a router or Layer 3 switch

  Why this is correct

  Inter-VLAN routing is the process of forwarding packets between different VLANs using a Layer 3 device such as a router or a multilayer switch. Because VLANs isolate broadcast domains, devices in different VLANs cannot communicate without this routing, which requires logical interfaces (subinterfaces or SVIs) and appropriate IP addressing. It is a fundamental concept that enables networks to combine segmentation with connectivity, but it is not a single switch configuration command.