Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
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?
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
Best answer
VLAN 30 is missing from the allowed VLAN list on the trunk.
That prevents VLAN 30 frames from reaching the distribution switch.
B
Distractor review
The user ports should be configured as trunks.
End-user ports should remain access ports.
C
Distractor review
The SVI for VLAN 30 must be shutdown for inter-VLAN routing to work.
An active SVI is required, not a shutdown one.
D
Distractor review
The trunk native VLAN must be changed to VLAN 30.
Native VLAN mismatch is not the issue shown.
Common exam trap
Common exam trap: answer the scenario, not the keyword
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.
Technical deep dive
How to think about this question
VLAN trunks are essential for carrying multiple VLAN traffic between switches, enabling devices in different VLANs to communicate through inter-VLAN routing. A trunk link uses tagging protocols like IEEE 802.1Q to identify VLAN frames as they traverse the link. If a VLAN is not allowed on the trunk, frames tagged with that VLAN ID are dropped and never reach the next switch or router, preventing communication beyond the local switch. In this scenario, the access switch hosts users in VLAN 30, but the trunk link to the distribution switch only allows VLANs 10 and 20. This restriction means VLAN 30 frames cannot cross the trunk, so users can communicate locally within VLAN 30 but cannot reach the default gateway SVI on the distribution switch. The correct resolution is to add VLAN 30 to the allowed VLAN list on the trunk interface, enabling inter-VLAN routing and gateway access. A common exam trap is confusing user access ports with trunk ports or misconfiguring the native VLAN. User ports should remain access ports assigned to a single VLAN, not trunks. Also, the native VLAN mismatch or SVI shutdown issues do not explain why VLAN 30 traffic is blocked on the trunk. Practically, understanding how VLAN tagging and allowed VLAN lists control traffic flow on trunks is critical for troubleshooting VLAN connectivity problems in Cisco networks.
KKey Concepts to Remember
- A trunk port forwards traffic for multiple VLANs by tagging frames with VLAN IDs using protocols like IEEE 802.1Q.
- The allowed VLAN list on a trunk interface determines which VLAN traffic is permitted to cross the trunk link.
- If a VLAN is not included in the trunk's allowed VLAN list, frames from that VLAN are dropped and do not reach other switches.
- Access ports connect end devices to a single VLAN and should not be configured as trunks in typical user scenarios.
- An active switched virtual interface (SVI) is required on a Layer 3 device to route traffic between VLANs and provide default gateway services.
- Native VLAN mismatches on trunks can cause untagged traffic issues but do not block tagged VLAN traffic from passing if allowed.
- Inter-VLAN routing depends on VLAN traffic successfully traversing trunks between access and distribution switches.
- Troubleshooting VLAN connectivity requires verifying trunk configuration, allowed VLAN lists, and SVI status on Layer 3 devices.
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 trunk port forwards traffic for multiple VLANs by tagging frames with VLAN IDs using protocols like IEEE 802.1Q.
What is the correct answer to this question?
The correct answer is: 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.
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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