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← 200-301
Full test
hardmultiple choiceObjective-mapped

Exhibit

SW1 Gi0/1 trunk allowed vlan 10,20
SW2 Gi0/1 trunk allowed vlan 10,20
Both switches have VLAN 30 configured and access ports assigned correctly.

Exhibit: Users on SW2 in VLAN 30 can reach local devices but not hosts in VLAN 30 on SW1. What is the most likely reason?

Question 1hardmultiple choice
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Exhibit: Users on SW2 in VLAN 30 can reach local devices but not hosts in VLAN 30 on SW1. What is the most likely reason?

Full question →

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 trunk native VLAN is 1 on both sides

Distractor.

B

Best answer

VLAN 30 is not allowed on the trunk

Correct choice.

C

Distractor review

SW2 must run VTP server mode

Distractor.

D

Distractor review

Spanning tree blocks all user VLANs by default

Distractor.

Common exam trap

Common exam trap: answer the scenario, not the keyword

A frequent exam trap is assuming that VLAN communication issues are caused by native VLAN mismatches or VTP mode settings. Candidates might incorrectly believe that if the native VLAN is the same on both sides, VLAN traffic should flow, or that VTP server mode is required for VLAN propagation. However, the real cause is often that the VLAN is simply not allowed on the trunk link. This misunderstanding leads to wasted time troubleshooting unrelated settings instead of checking the allowed VLAN list on the trunk interface.

Technical deep dive

How to think about this question

VLAN trunks are essential in Cisco switched networks to carry traffic for multiple VLANs over a single physical link. The IEEE 802.1Q standard tags Ethernet frames with VLAN identifiers, allowing switches to distinguish and forward frames to the correct VLAN. Each switch port configured as a trunk can carry traffic for multiple VLANs simultaneously, enabling devices in the same VLAN but on different switches to communicate as if they were on the same Layer 2 segment. For VLAN traffic to traverse a trunk link, the trunk must be configured to allow the VLANs that need to communicate. By default, Cisco switches allow all VLANs on a trunk, but administrators can restrict allowed VLANs for security or traffic management. If a VLAN is not included in the allowed VLAN list on the trunk, frames tagged with that VLAN ID will be dropped at the trunk interface, preventing inter-switch communication for that VLAN. This is why even if VLAN 30 exists on both switches, hosts in VLAN 30 cannot communicate if VLAN 30 is not allowed on the trunk. A common exam trap is confusing the native VLAN or VTP mode with VLAN allowance on trunks. The native VLAN is untagged traffic on a trunk and does not control which VLANs are allowed. VTP server mode manages VLAN database synchronization but does not affect trunk VLAN allowance directly. Additionally, STP blocks ports to prevent loops but does not block all VLANs by default. Understanding that VLAN allowance on trunks directly controls VLAN traffic flow is critical for troubleshooting and exam success.

KKey Concepts to Remember

  • A VLAN trunk link carries traffic for multiple VLANs between switches by tagging frames with VLAN identifiers using IEEE 802.1Q encapsulation.
  • A trunk port must be configured to allow all VLANs that need to communicate across switches; otherwise, VLAN traffic not allowed on the trunk is blocked.
  • Switches maintain local VLAN databases, but VLANs must be permitted on trunks to enable inter-switch VLAN communication.
  • The native VLAN on a trunk is untagged by default and does not affect VLAN traffic forwarding unless mismatched, but it is unrelated to VLAN allowance.
  • VTP server mode controls VLAN database propagation but does not affect VLAN traffic forwarding on trunks directly.
  • Spanning Tree Protocol (STP) selectively blocks ports to prevent loops but does not block all user VLANs by default.
  • When VLAN traffic cannot pass between switches, the most common cause is that the VLAN is not allowed on the trunk link.
  • Trunk configuration errors are a frequent cause of VLAN connectivity issues in multi-switch environments.

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 trunk link carries traffic for multiple VLANs between switches by tagging frames with VLAN identifiers using IEEE 802.1Q encapsulation.

What is the correct answer to this question?

The correct answer is: VLAN 30 is not allowed on the trunk — The trunk is allowing only VLANs 10 and 20. Even though both switches have VLAN 30 defined locally, VLAN 30 traffic cannot cross the trunk unless that VLAN is allowed on the link.

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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