Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A trunk link between two switches is up, but voice phones connected through one access switch no longer receive the correct voice VLAN treatment. Data users still pass traffic. Which area should be checked first?
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
Whether the voice VLAN is being carried and handled correctly across the switching path.
This is correct because selective failure affecting phones points to voice-VLAN handling rather than complete link failure.
B
Distractor review
Whether OSPFv3 neighbors are fully adjacent on the phone switch ports.
This is wrong because OSPFv3 is not the primary issue in voice-VLAN handling on access ports.
C
Distractor review
Whether the wireless controller has the correct guest SSID.
This is wrong because the scenario is wired voice/data switching, not WLAN guest access.
D
Distractor review
Whether BGP uses a lower metric than the static route.
This is wrong because the symptom is Layer 2 voice-VLAN treatment, not interdomain routing.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is to confuse Layer 2 VLAN issues with Layer 3 routing problems. Candidates may incorrectly check OSPFv3 neighbor adjacency or BGP route metrics, which do not affect voice VLAN tagging or traffic prioritization on access switch ports. Another trap is to consider wireless controller configurations, which are irrelevant in wired voice VLAN scenarios. The key mistake is assuming the trunk link being up means all VLANs are correctly carried, ignoring that the voice VLAN might be missing or misconfigured on the trunk or access ports, causing selective failure of voice traffic while data traffic continues.
Technical deep dive
How to think about this question
A voice VLAN is a specialized VLAN configured on switches to separate voice traffic from data traffic, ensuring Quality of Service (QoS) and proper prioritization for IP phones. When a voice VLAN is configured, the switch tags voice traffic with the appropriate VLAN ID, allowing switches and routers to recognize and prioritize voice packets. This separation prevents voice traffic from being delayed or dropped due to congestion on the data VLAN, which is critical for maintaining call quality. In troubleshooting scenarios where the trunk link between switches is operational but voice phones lose correct VLAN treatment, the first step is to verify that the voice VLAN is being carried end-to-end across the switching path. This includes checking trunk configurations to ensure the voice VLAN is allowed and properly tagged, verifying switchport configurations on access switches for voice VLAN settings, and confirming that QoS policies are applied correctly. Data VLAN traffic may continue to flow normally because it is handled separately, so the issue is isolated to voice VLAN handling rather than a total link failure. A common exam trap is to focus on unrelated protocols or routing issues such as OSPFv3 adjacency or BGP metrics, which do not affect Layer 2 VLAN tagging and voice traffic prioritization. Another mistake is to consider wireless controller settings irrelevant to wired voice VLAN problems. Practically, voice VLAN misconfigurations often manifest as selective service failures where data traffic works but voice traffic does not, emphasizing the need to check VLAN tagging and trunk configurations first.
KKey Concepts to Remember
- A voice VLAN separates voice traffic from data traffic to ensure Quality of Service and proper prioritization on Cisco switches.
- Switches tag voice traffic with the voice VLAN ID to maintain traffic separation and enable correct forwarding across the network.
- Trunk links must be configured to carry the voice VLAN alongside data VLANs to allow voice traffic to traverse multiple switches.
- Access switch ports connected to IP phones must be configured with the correct voice VLAN to tag voice packets properly.
- Data VLAN traffic can continue to pass normally even if the voice VLAN is misconfigured or blocked on the trunk.
- Troubleshooting voice VLAN issues requires verifying VLAN tagging and trunk configurations before considering routing or wireless factors.
- OSPFv3 adjacency and BGP routing metrics do not impact Layer 2 voice VLAN tagging or voice traffic handling on access switches.
- Selective failure of voice services with normal data traffic indicates a problem specific to voice VLAN handling rather than total link failure.
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.
Related practice questions
Related 200-301 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
CCNA subnetting practice questions
Practise IPv4 subnetting, CIDR, masks, host ranges and subnet selection.
CCNA OSPF practice questions
Practise OSPF neighbours, router IDs, metrics, areas and routing-table interpretation.
CCNA VLAN practice questions
Practise VLANs, access ports, trunks, allowed VLANs and switching scenarios.
CCNA STP practice questions
Practise spanning tree, root bridge election, port roles and STP troubleshooting.
CCNA EtherChannel practice questions
Practise LACP, PAgP, port-channel behaviour and bundle requirements.
CCNA ACL practice questions
Practise standard and extended ACLs, permit/deny logic and traffic filtering.
CCNA NAT practice questions
Practise static NAT, dynamic NAT, PAT and inside/outside address translation.
CCNA DHCP practice questions
Practise DHCP scopes, relay, leases and troubleshooting.
CCNA show ip route practice questions
Practise routing-table output, longest-prefix match, AD and route selection.
CCNA show interfaces trunk practice questions
Practise trunk verification and VLAN forwarding across switches.
CCNA wireless security practice questions
Practise WLAN security, authentication and wireless architecture concepts.
CCNA IPv6 practice questions
Practise IPv6 addressing, routes, neighbour discovery and common IPv6 exam traps.
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 voice VLAN separates voice traffic from data traffic to ensure Quality of Service and proper prioritization on Cisco switches.
What is the correct answer to this question?
The correct answer is: Whether the voice VLAN is being carried and handled correctly across the switching path. — The first area to check is the end-to-end handling of the voice VLAN across the switching path. In practical terms, the data VLAN can still work while the voice VLAN experiences a forwarding, configuration, or policy problem. Because the phones depend on the correct voice VLAN behavior, that VLAN path should be examined first rather than assuming the whole trunk is broken. This is a selective-services troubleshooting question. One class of traffic can fail even when ordinary user data still works.
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.
Discussion
Loading comments…
Sign in to join the discussion.