N10-009 Network Implementation 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 trunk is using 802.1Q encapsulation and the remote switch expects ISL

  Why it's wrong here

  An encapsulation mismatch, such as one switch expecting 802.1Q and the other ISL, would fundamentally prevent the trunk link from establishing or passing any traffic reliably. This severe incompatibility would manifest as the trunk port failing to come up or remaining in an error-disabled state, rather than allowing the trunk to form and then only generating errors specifically related to native VLAN tagging on certain frames.

  When this WOULD be correct

  A switch port configured as a trunk using 802.1Q on one side and ISL on the other would cause errors because the encapsulation types are incompatible. This would be the correct answer if the question described a trunk link with mismatched encapsulation protocols.

• ✗

  The remote switch is sending frames on VLAN 99 as untagged

  Why it's wrong here

  When a switch port is configured with a native VLAN, it expects frames belonging to that VLAN to arrive untagged. If the remote switch correctly sends untagged frames for VLAN 99, the local switch would process them without error, as this is the standard behavior for 802.1Q native VLANs. Therefore, this scenario would not cause the reported error condition, which implies a problem with frame handling.

  When this WOULD be correct

  This option would be correct if the question described a scenario where a trunk port is configured with native VLAN 99, but the remote switch is sending frames on VLAN 99 as untagged, causing a mismatch because the local switch expects them to be tagged (e.g., if the native VLAN is not VLAN 99 on the remote side).

• ✓

  The remote switch is tagging frames on the native VLAN

  Why this is correct

  When a trunk is configured with native VLAN 99, frames for that VLAN should be sent untagged. If the remote switch sends them tagged, the receiving switch may log errors or drop the frames because it expects untagged frames for the native VLAN.

• ✗

  The allowed VLAN list does not include VLAN 99

  Why it's wrong here

  If VLAN 99 were not included in the allowed VLAN list on the local trunk port, any frames received for VLAN 99, whether tagged or untagged, would be silently dropped by the switch. This action is a filtering function, not a tagging mismatch error. The switch would not generate an error indicating a native VLAN tagging issue but rather discard the frames without further processing or a specific native VLAN error.

  When this WOULD be correct

  This option would be correct if the question described that frames on VLAN 99 are being dropped or not forwarded, and the trunk configuration explicitly denies VLAN 99 in the allowed VLAN list, or if the switch displays an error indicating VLAN 99 is not allowed on the trunk.

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 N10-009 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official N10-009blueprint 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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