Question 1,806 of 1,389
CCNA Network Services and Security Practice Question
Exhibit
Access-SW uplink: interface g0/24 switchport mode trunk switchport trunk allowed vlan 10,20 User ports: interface range g0/1-12 switchport mode access switchport access vlan 30 Distribution switch SVI: interface vlan 30 ip address 10.30.30.1 255.255.255.0
Users on a new access switch can reach devices in their own VLAN but cannot reach the default gateway on the distribution switch. Based on the exhibit, what is the most likely cause?
⚠ Common exam trap
A common exam trap is assuming that user ports must be trunks to enable VLAN communication beyond the local switch. In reality, user ports should remain access ports assigned to a single VLAN. Another trap is thinking that the SVI for VLAN 30 must be shut down to fix routing issues, but an active SVI is necessary for inter-VLAN routing. Additionally, candidates may incorrectly focus on native VLAN mismatches, which do not block VLAN 30 traffic if the VLAN is not allowed on the trunk. The real issue is the missing VLAN 30 in the trunk's allowed VLAN list, which prevents VLAN 30 frames from reaching the distribution switch and the default gateway.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
VLAN 30 is missing from the allowed VLAN list on the trunk.
The trunk allows only VLANs 10 and 20, so VLAN 30 traffic never crosses the uplink. Local switching inside VLAN 30 on the access switch can still work, which is why same-VLAN communication succeeds. Adding VLAN 30 to the allowed list is the direct fix.
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 missing from the allowed VLAN list on the trunk.
Why this is correct
On a trunk, a VLAN must be present in the allowed VLAN list for its frames to traverse the link. If VLAN 30 was not explicitly added to the allowed list, frames from that VLAN are dropped at the trunk port, so they never reach the distribution switch. This prevents inter-VLAN routing even though local hosts within VLAN 30 on the access switch can communicate. Adding 'allowed vlan add 30' to the trunk configuration restores connectivity.
- ✗
The user ports should be configured as trunks.
Why it's wrong here
End-user devices expect a single untagged VLAN on an access port, not a trunk that carries multiple VLANs. Configuring user ports as trunks would not help VLAN 30 reach the distribution switch; it could actually allow users to access other VLANs or cause VLAN hopping security issues. The proper design is to keep user ports as access ports in VLAN 30 and ensure the uplink trunk carries VLAN 30 to the distribution switch.
When this WOULD be correct
In a different scenario where users need to connect multiple VLANs on a single port, such as in a network with multiple VLANs on a single access switch, configuring user ports as trunks would be necessary to allow traffic from multiple VLANs to traverse the same port.
- ✗
The SVI for VLAN 30 must be shutdown for inter-VLAN routing to work.
Why it's wrong here
A shutdown SVI would disable the Layer 3 interface for VLAN 30, making inter-VLAN routing impossible for that VLAN. The problem described is that hosts reach their own VLAN but cannot reach other VLANs, which points to a Layer 2 trunk filtering issue, not a down SVI. For routing to occur, the SVI must be in an up/up state and have a valid IP address; shutting it down is the opposite of the required condition.
When this WOULD be correct
In a scenario where the question states that VLAN 30 is configured but the SVI for VLAN 30 is administratively down, the option would be correct. This would indicate that users in VLAN 30 cannot route traffic to the default gateway because the SVI is not active.
- ✗
The trunk native VLAN must be changed to VLAN 30.
Why it's wrong here
The native VLAN on a trunk is used for untagged traffic (typically VLAN 1 by default) and is not related to which VLANs are allowed across the link. Changing the native VLAN to 30 would not cause VLAN 30 frames to be forwarded if VLAN 30 is not in the allowed list; furthermore, inconsistent native VLANs on both ends could cause a native VLAN mismatch and disrupt all trunk traffic. The root cause is the missing allowed VLAN entry, not the native VLAN setting.
When this WOULD be correct
In a different scenario where the question states that users are unable to communicate with devices in other VLANs due to misconfigured native VLAN settings, changing the trunk native VLAN to VLAN 30 could resolve issues with untagged traffic being misrouted.
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.
✓VLAN 30 is missing from the allowed VLAN list on the trunk.Correct answer▾
Why this is correct
On a trunk, a VLAN must be present in the allowed VLAN list for its frames to traverse the link. If VLAN 30 was not explicitly added to the allowed list, frames from that VLAN are dropped at the trunk port, so they never reach the distribution switch. This prevents inter-VLAN routing even though local hosts within VLAN 30 on the access switch can communicate. Adding 'allowed vlan add 30' to the trunk configuration restores connectivity.
✗The user ports should be configured as trunks.Wrong answer — click to see why▾
Why this is wrong here
User ports should be configured as access ports, not trunks, to ensure they can communicate within their VLAN without unnecessary complexity. Configuring them as trunks would not resolve the issue of reaching the default gateway.
★ When this WOULD be the correct answer
In a different scenario where users need to connect multiple VLANs on a single port, such as in a network with multiple VLANs on a single access switch, configuring user ports as trunks would be necessary to allow traffic from multiple VLANs to traverse the same port.
Why candidates choose this
Candidates may confuse the need for VLAN communication with the concept of trunking, mistakenly believing that user ports should be set as trunks to facilitate access to the default gateway.
✗The SVI for VLAN 30 must be shutdown for inter-VLAN routing to work.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the SVI (Switched Virtual Interface) for VLAN 30 being shut down would not prevent users in VLAN 30 from reaching their default gateway; rather, it would affect inter-VLAN routing. The issue in the original question is related to trunk configuration, not SVI status.
★ When this WOULD be the correct answer
In a scenario where the question states that VLAN 30 is configured but the SVI for VLAN 30 is administratively down, the option would be correct. This would indicate that users in VLAN 30 cannot route traffic to the default gateway because the SVI is not active.
Why candidates choose this
Candidates may choose this option because they understand the importance of SVIs in routing and might mistakenly believe that a shutdown SVI would directly impact connectivity to the default gateway for devices in the same VLAN.
✗The trunk native VLAN must be changed to VLAN 30.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because changing the trunk native VLAN to VLAN 30 does not address the issue of users not reaching the default gateway; it only affects untagged traffic on the trunk link.
★ When this WOULD be the correct answer
In a different scenario where the question states that users are unable to communicate with devices in other VLANs due to misconfigured native VLAN settings, changing the trunk native VLAN to VLAN 30 could resolve issues with untagged traffic being misrouted.
Why candidates choose this
Candidates may find this option tempting because they might confuse native VLAN settings with VLAN communication issues, thinking that adjusting the native VLAN could resolve routing problems between VLANs.
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?”
Visual reference
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Last reviewed: May 17, 2026
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