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.

• ✗

  802.1Q trunking is a Cisco-proprietary protocol that uses a 4-byte tag to identify VLAN membership.

  Why it's wrong here

  802.1Q is an IEEE standardized trunking protocol, not a Cisco-proprietary one. It does use a 4-byte tag, but the tag's structure is defined by the open standard, and the proprietary alternative is ISL (Inter-Switch Link), which is a Cisco legacy protocol that wraps frames with a 26-byte header. Hence, the statement incorrectly conflates 802.1Q with ISL, making it wrong.

• ✓

  By default, frames belonging to the native VLAN are sent untagged across an 802.1Q trunk.

  Why this is correct

  On an 802.1Q trunk, the native VLAN is deliberately transmitted without any VLAN tag. The receiving switch assumes that any untagged frame arriving on the trunk belongs to its configured native VLAN, which is why the administrator must ensure the native VLAN matches on both ends. This untagged behavior permits interoperability with devices that do not understand 802.1Q tagging and is enforced by default.

• ✗

  Inter-VLAN routing can be accomplished using a Layer 2 switch configured with VLAN access maps.

  Why it's wrong here

  Inter-VLAN routing requires a Layer 3 device, such as a router or a Layer 3 switch, to forward packets between different VLAN subnets. VLAN access maps (VACLs) are purely Layer 2 filtering mechanisms that control traffic within a single VLAN based on MAC addresses or other L2 criteria; they do not possess routing capabilities. Therefore, relying on VACLs alone cannot accomplish inter-VLAN routing, making this option incorrect.

• ✓

  The native VLAN must be identical on both ends of an 802.1Q trunk to avoid native VLAN mismatch errors.

  Why this is correct

  For an 802.1Q trunk to function correctly, the native VLAN must be configured identically on both connected switches. If the native VLANs differ, untagged frames received on a trunk are placed into the local native VLAN, which can cause traffic from one VLAN to be improperly forwarded into another and create security vulnerabilities. Cisco switches also use CDP or LLDP to send error messages when a native VLAN mismatch is detected, so this statement is correct.

• ✗

  Switches strip the 802.1Q tag from all frames before forwarding them out of a trunk port.

  Why it's wrong here

  On an 802.1Q trunk, frames from non-native VLANs retain their 4-byte tag as they travel across the trunk link, precisely so the receiving switch can identify each frame's VLAN. The tag is stripped off only when the frame exits an access port assigned to that VLAN, or for native VLAN frames it is initially sent untagged. Hence, claiming that switches strip tags from all frames before forwarding out a trunk port contradicts the fundamental purpose of trunking, making the option incorrect.

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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