CCNA Switching and Network Access Practice Question
Exhibit
SW1# show vlan brief 60 Users-60 active SW2# show vlan brief 10 Users-10 active 20 Users-20 active SW2# show interfaces trunk Port Mode Encapsulation Status Native vlan Gi0/1 on 802.1q trunking 1 Port Vlans allowed on trunk Gi0/1 10,20,60
Users in VLAN 60 on switch SW2 cannot reach the default gateway located on switch SW1. The trunk between SW1 and SW2 is operational and allows VLAN 60. What is the most likely reason for this issue?
⚠ Common exam trap
Don't assume trunk configuration alone resolves VLAN issues; ensure VLANs exist on all relevant switches.
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 60 does not exist locally on SW2.
VLAN 60 has not been created locally on SW2, even though the trunk can carry its traffic. A switch never processes VLAN traffic for a VLAN it doesn't know about; it discards tagged frames from the trunk destined for that VLAN and prevents access ports from assigning frames to it. (A) is correct. (B) is incorrect because native VLAN configuration only affects untagged frames—changing it to 60 is unnecessary for tagged VLAN 60 traffic. (C) is incorrect because the trunk is already configured to allow VLAN 60, so trunk filtering isn't the problem. (D) is incorrect because a default gateway is simply an IP address on a router or Layer 3 switch interface (like SVIs) and does not require a loopback on SW2.
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 60 does not exist locally on SW2.
Why this is correct
This is the most likely reason: SW2 has not been created with VLAN 60, so it does not have a spanning-tree instance or a switch virtual interface for that VLAN. Even if the trunk port with SW1 allows VLAN 60 and receives tagged frames, those frames are discarded because the VLAN is not present in SW2's VLAN database. Consequently, users in VLAN 60 cannot communicate through SW2, and no access port or SVI can be assigned to that VLAN.
- ✗
The native VLAN must be changed to 60 on both switches.
Why it's wrong here
This is incorrect because the native VLAN is used for untagged frames on an 802.1Q trunk, and changing the native VLAN to 60 would not create VLAN 60 on SW2. The problem is that SW2 has no VLAN 60 in its configuration, so even if the native VLAN matched, there would be no local VLAN to carry the traffic. Additionally, using VLAN 60 as the native VLAN could actually cause mismatched native VLAN errors if the other switch expects a different native VLAN, making this a separate misconfiguration rather than the root cause.
When this WOULD be correct
In a different scenario where the question asks about VLAN configuration issues related to untagged traffic, changing the native VLAN to 60 could be necessary to ensure that devices on VLAN 60 can communicate properly with devices on other VLANs that are also configured to use the same native VLAN.
- ✗
VLAN 60 is not allowed on the trunk link.
Why it's wrong here
While a trunk can restrict VLANs via the allowed list, the exhibit likely shows VLAN 60 permitted on the trunk between SW1 and SW2. Even if it were not, the absence of VLAN 60 from SW2's local database would still prevent traffic from being forwarded, making this option an incorrect explanation. The reference to PPP is a red herring because PPP is a serial encapsulation and has nothing to do with 802.1Q VLAN forwarding.
When this WOULD be correct
In a different scenario, if the question specified that only PPP encapsulation is allowed for VLANs on a trunk link, then this option could be correct. For example, if the question stated that VLANs are only operational when PPP is configured on the trunk, then this option would apply.
- ✗
The default gateway must be configured as a loopback on SW2.
Why it's wrong here
This is incorrect because the default gateway for end users is typically configured on the switch virtual interface (SVI) for VLAN 60, not as a loopback. A loopback interface is a logical router interface used for management or routing protocol stability, but it would not serve as the default gateway for hosts in a specific VLAN. The actual fault is that SW2 does not have VLAN 60 defined, so no SVI can be created for it, and the hosts cannot reach their gateway.
When this WOULD be correct
In a different scenario where the question specifies that the network design requires the default gateway to be a loopback interface for redundancy or routing purposes, this option could be correct. For instance, if the exam question states that SW2 must use a loopback interface for routing protocols, then this option would be valid.
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 60 does not exist locally on SW2.Correct answer▾
Why this is correct
This is the most likely reason: SW2 has not been created with VLAN 60, so it does not have a spanning-tree instance or a switch virtual interface for that VLAN. Even if the trunk port with SW1 allows VLAN 60 and receives tagged frames, those frames are discarded because the VLAN is not present in SW2's VLAN database. Consequently, users in VLAN 60 cannot communicate through SW2, and no access port or SVI can be assigned to that VLAN.
✗The native VLAN must be changed to 60 on both switches.Wrong answer — click to see why▾
Why this is wrong here
The native VLAN is used for untagged traffic on a trunk and is typically VLAN 1 by default. Changing the native VLAN to 60 would not resolve the issue because the problem is that VLAN 60 does not exist on SW2, not that the native VLAN is mismatched. Native VLAN mismatch can cause connectivity issues but is unrelated to the absence of the VLAN.
★ When this WOULD be the correct answer
In a different scenario where the question asks about VLAN configuration issues related to untagged traffic, changing the native VLAN to 60 could be necessary to ensure that devices on VLAN 60 can communicate properly with devices on other VLANs that are also configured to use the same native VLAN.
Why candidates choose this
Students often confuse the native VLAN with the VLAN that carries user traffic. They might think that setting the native VLAN to 60 would allow VLAN 60 traffic to pass, but native VLAN is only for untagged frames and does not affect tagged VLAN forwarding.
✗VLAN 60 is not allowed on the trunk link.Wrong answer — click to see why▾
Why this is wrong here
The trunk is specifically configured to allow VLAN 60, so this cannot be the cause.
★ When this WOULD be the correct answer
In a different scenario, if the question specified that only PPP encapsulation is allowed for VLANs on a trunk link, then this option could be correct. For example, if the question stated that VLANs are only operational when PPP is configured on the trunk, then this option would apply.
Why candidates choose this
Test-takers might confuse PPP with a protocol that can carry multiple VLANs, but PPP is a layer 2 protocol for point-to-point links and does not support VLANs. The mention of 'PPP' might be mistaken for 'P' in '802.1Q' or a similar acronym.
✗The default gateway must be configured as a loopback on SW2.Wrong answer — click to see why▾
Why this is wrong here
The default gateway is typically configured on a router or Layer 3 switch, not as a loopback interface on the access switch. A loopback interface is a virtual interface used for management or routing protocol stability, not for providing a default gateway to hosts. The issue is VLAN existence, not gateway design.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that the network design requires the default gateway to be a loopback interface for redundancy or routing purposes, this option could be correct. For instance, if the exam question states that SW2 must use a loopback interface for routing protocols, then this option would be valid.
Why candidates choose this
Students might think that a loopback interface can serve as a default gateway because it is always up. However, the default gateway must be on the same subnet as the hosts and reachable via the VLAN. Configuring a loopback on SW2 would not provide connectivity to SW1's gateway.
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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Written by Johnson Ajibi, MSc IT Security
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