Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Exhibit
SW1# show interfaces trunk Port Mode Encapsulation Status Native vlan Gi1/0/24 on 802.1q trunking 1 Port Vlans allowed on trunk Gi1/0/24 10,20,40 Port Vlans in spanning tree forwarding state and not pruned Gi1/0/24 10,20,40
Exhibit: Users in VLAN 30 cannot reach devices in other VLANs after a switch replacement. What is the most likely cause?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
The native VLAN must be changed to 30
A native VLAN mismatch is a different issue and does not specifically explain why only VLAN 30 is failing here.
B
Best answer
VLAN 30 is not permitted on the trunk link
The trunk allowed list does not include VLAN 30.
C
Distractor review
The uplink should be configured as an access port
Switch uplinks carrying multiple VLANs should remain trunks.
D
Distractor review
STP must be disabled on VLAN 30
Disabling STP would be dangerous and would not fix a missing trunk allowance.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is to confuse the native VLAN mismatch with VLAN trunk allowed list issues. Native VLAN mismatches cause untagged traffic to be misinterpreted but do not block a specific VLAN’s traffic entirely. Another trap is thinking the uplink should be an access port to isolate VLAN traffic, which actually prevents multiple VLANs from traversing the link and breaks inter-VLAN routing. Candidates may also incorrectly assume changing the native VLAN to 30 fixes the problem, but this does not affect VLAN tagging or trunk permissions. The key is understanding that VLAN 30 traffic is blocked because it is not permitted on the trunk, not because of native VLAN or port mode settings.
Technical deep dive
How to think about this question
VLANs (Virtual Local Area Networks) logically segment a physical network into multiple broadcast domains, allowing devices in different VLANs to communicate only through a Layer 3 device or inter-VLAN routing. Switch ports assigned to a VLAN forward traffic only for that VLAN, and trunk links carry traffic for multiple VLANs between switches by tagging frames with VLAN identifiers using protocols like IEEE 802.1Q. When a trunk link is configured between switches, it must be allowed to carry traffic for all VLANs that need to communicate across the link. Cisco switches use a trunk allowed VLAN list to control which VLANs are permitted on the trunk. If a VLAN is not included in this allowed list, frames tagged with that VLAN ID are dropped on the trunk, preventing devices in that VLAN from reaching other VLANs or networks beyond the switch. The exam trap here is confusing VLAN trunking issues with native VLAN mismatches or port mode misconfigurations. While native VLAN mismatches cause untagged traffic problems, they do not selectively block a single VLAN’s traffic. Similarly, configuring an uplink as an access port disables VLAN tagging and restricts traffic to a single VLAN, which is incorrect for inter-VLAN communication. The practical impact is that users in VLAN 30 cannot reach other VLANs because their traffic never crosses the trunk link due to VLAN 30 being excluded from the allowed VLAN list.
KKey Concepts to Remember
- A VLAN segments a network into separate broadcast domains, requiring inter-VLAN routing for communication between VLANs.
- Trunk links carry traffic for multiple VLANs by tagging frames with VLAN IDs using 802.1Q encapsulation.
- The trunk allowed VLAN list controls which VLANs are permitted to send traffic across a trunk link between switches.
- If a VLAN is not permitted on a trunk, traffic from that VLAN is dropped and cannot reach other VLANs or networks beyond the trunk.
- Native VLAN mismatches cause untagged traffic issues but do not selectively block traffic from a specific VLAN like VLAN 30.
- Configuring an uplink as an access port restricts traffic to a single VLAN and prevents inter-VLAN communication over that link.
- Switches forward VLAN-tagged frames only if the VLAN is allowed on the trunk, ensuring proper segmentation and traffic flow.
- Inter-VLAN communication depends on both correct VLAN membership on access ports and proper VLAN allowance on trunk links.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
A VLAN segments a network into separate broadcast domains, requiring inter-VLAN routing for communication between VLANs.
What is the correct answer to this question?
The correct answer is: VLAN 30 is not permitted on the trunk link — The trunk is up, but VLAN 30 is not allowed on it. Traffic from that VLAN never crosses the uplink, so inter-VLAN reachability fails for users in VLAN 30 even though the local access ports may still look fine.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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