CCNP Practice Question: An engineer is troubleshooting a connectivity…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  VLAN 30 is not created in the VLAN database on SW2.

  Why this is correct

  VLAN 30 is not created in the VLAN database on SW2. A trunk link will forward frames for a VLAN only if that VLAN exists in the local VLAN database of the switch; otherwise the switch drops the frames as ingress/egress filtering prevents unknown VLANs from crossing the trunk. Even though SW1 has VLAN 30 configured and the allowed list on SW2 may include VLAN 30 by default, SW2 cannot pass frames for a VLAN it does not know. Creating VLAN 30 on SW2 (or using VTP to propagate it) is required for end-to-end connectivity.

• ✗

  The native VLAN is mismatched between SW1 and SW2.

  Why it's wrong here

  The native VLAN is mismatched between SW1 and SW2. This would cause control-plane issues such as STP BPDUs being exchanged on mismatched native VLANs, and user traffic on the native VLAN could leak or be misdirected between the two switches. However, VLAN 30 is a specific non-native VLAN in this scenario; traffic on VLAN 30 is encapsulated with an 802.1Q tag and is unaffected by the native VLAN setting. Thus, a native VLAN mismatch would not single out VLAN 30 as having no connectivity while other non-native VLANs work.

• ✗

  VTP pruning is removing VLAN 30 from the trunk.

  Why it's wrong here

  VTP pruning is removing VLAN 30 from the trunk. If VTP pruning were active, VLAN 30 would be pruned only on a trunk interface when the switch on the other end has no ports in that VLAN; however, pruning does not remove a VLAN from the VLAN database, it merely removes the VLAN from the allowed list on the trunk. The option states VLAN 30 does not appear in the allowed list, which is a possible symptom, but VTP pruning requires VTP transparency or client/server propagation and would prune VLANs globally based on the absence of ports, not just on one trunk. Additionally, VTP pruning is disabled by default on Cisco switches, and the question does not indicate it was enabled, making this an unlikely root cause.

• ✗

  The trunk is not forming due to DTP negotiation.

  Why it's wrong here

  The trunk is not forming due to DTP negotiation. Both SW1 and SW2 are shown with the interface mode set to 'trunk' (static trunk), which is a DTP mode that always sends DTP frames and actively forms a trunk regardless of the remote side's mode as long as the remote is not in access mode. Since both sides are configured as trunk mode, DTP negotiation will succeed and the trunk will form unless there is an administrative reason (like an allowed VLAN list or VLAN database issue) preventing traffic. Therefore, the trunk itself is operational; the problem is limited to VLAN 30 crossing the already-established trunk.