Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Exhibit
interface Gi1/0/7 switchport mode access switchport voice vlan 20 spanning-tree portfast
Exhibit: A phone and a PC are attached to the same switchport. The phone works, but the PC cannot reach the data network. Which switch setting is most likely missing?
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
switchport mode dynamic auto
Dynamic auto is not the standard requirement for an endpoint-facing phone port.
B
Distractor review
switchport voice vlan 20
The phone is already working, so the voice VLAN likely exists.
C
Best answer
switchport access vlan 10
The PC needs the correct data VLAN assignment on the access side.
D
Distractor review
spanning-tree guard root
Root Guard is unrelated to this symptom.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is focusing only on the voice VLAN configuration because the IP phone works, leading to the mistaken belief that the port is fully configured. However, the PC sends untagged frames that require a proper access VLAN assignment. Without the switchport access vlan command, the PC's traffic is not placed into the correct VLAN, causing data network failure. Candidates might also incorrectly select dynamic auto mode, thinking it enables device connectivity, but this mode is for trunk negotiation and not suitable for endpoint ports. Misunderstanding these details causes candidates to overlook the missing access VLAN, resulting in incorrect answers.
Technical deep dive
How to think about this question
When a Cisco IP phone and a PC share a single switchport, the switch must handle two types of traffic: voice and data. The phone typically tags its voice traffic with a specific VLAN ID known as the voice VLAN, while the PC sends untagged frames that belong to the data VLAN. This separation allows the switch to apply different policies such as Quality of Service (QoS) for voice traffic and standard forwarding for data traffic. The switchport voice VLAN command configures the VLAN for tagged voice frames, and the switchport access VLAN command assigns the VLAN for untagged data frames from the PC. The decision process for configuring such a port involves ensuring that the voice VLAN is set for the IP phone and that the access VLAN is correctly assigned for the PC. If the voice VLAN is configured but the access VLAN is missing or incorrect, the phone will still register and function because its traffic is tagged and recognized. However, the PC's untagged frames will not be assigned to the correct VLAN, causing it to fail to reach the data network. Dynamic auto mode is irrelevant here because endpoint ports typically operate as access ports, not trunks. Similarly, spanning-tree root guard does not influence VLAN assignment or endpoint connectivity. A common exam trap is assuming that configuring the voice VLAN alone is sufficient for both devices to work. Candidates often overlook the need for the access VLAN, which leads to the PC failing to communicate despite the phone working. In practical networks, this misconfiguration causes user complaints about data connectivity while voice remains operational. Understanding that the access VLAN handles untagged PC traffic and the voice VLAN handles tagged phone traffic is crucial to avoid this mistake and ensure both devices function correctly on the same port.
KKey Concepts to Remember
- A Cisco switchport configured for an IP phone and PC must have both a voice VLAN and a data VLAN to separate voice and data traffic properly.
- The switchport access VLAN setting assigns the VLAN for untagged data traffic from devices like PCs connected behind an IP phone.
- The switchport voice VLAN command assigns a special VLAN for tagged voice traffic from Cisco IP phones, enabling QoS and traffic separation.
- If the voice VLAN is configured but the access VLAN is missing or incorrect, the phone can function while the PC cannot access the data network.
- Dynamic auto mode on a switchport allows the port to negotiate trunking but is not required or recommended for endpoint ports with IP phones.
- Spanning-tree root guard protects the root bridge placement in STP and does not affect VLAN assignment or endpoint connectivity on access ports.
- Cisco IP phones tag voice traffic with the voice VLAN ID, while PCs send untagged frames that must be assigned to the correct access VLAN.
- Proper VLAN configuration on switchports ensures that voice and data traffic are separated and forwarded correctly, preventing connectivity issues.
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 Cisco switchport configured for an IP phone and PC must have both a voice VLAN and a data VLAN to separate voice and data traffic properly.
What is the correct answer to this question?
The correct answer is: switchport access vlan 10 — When a Cisco IP phone and a PC share one port, the switchport often needs both a data VLAN and a voice VLAN. If the voice VLAN exists but the data access VLAN is wrong or missing, the phone can work while the PC fails.
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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