Trunking & Voice VLANs

Covers Lesson 3 and Lesson 4

Checks whether you can carry VLANs between switches and, crucially, tell the two trunk faults apart — they look nothing alike once you know what to compare.

Topics covered

• 802.1Q tagging and the native VLAN
• Native-VLAN mismatch versus allowed-list mismatch
• DTP modes and why two autos never trunk
• The phone-plus-PC port and its two VLANs

Every question here is answerable from the first-party notes of the lessons above. You commit to an answer before you see whether it was right.

This quiz is a Week 3 milestone in its own right. Passing it does not change the completion state of any individual lesson, and you do not need it to finish the lessons it covers.

Section quiz

Trunking & Voice VLANs

8 questions covering Lesson 3 and Lesson 4. Answer each one before you see whether you were right.

Question 1 of 8

1. How large is the 802.1Q tag, and how wide is the VLAN ID field inside it?

2. Which VLAN travels untagged across an 802.1Q trunk, and what is its default?

3. SW1 has native vlan 1 on its trunk and SW2 has native vlan 99. What is the symptom, and where do you confirm it?

4. VLAN 20 cannot cross a trunk while VLAN 10 works fine, and no CDP mismatch is logged. What is the most likely fault?

5. You need to add VLAN 20 to a trunk that already allows VLAN 10. Which command is correct?

6. Both ends of a switch-to-switch link are left in switchport mode dynamic auto. What is the result?

7. A PC plugs into the back of an IP phone, and the phone plugs into one switch port. The PC is in data VLAN 10 and the phone in voice VLAN 110. What kind of port is this?

8. How does the IP phone learn which VLAN to tag its call traffic into?

Back to Lesson 4 Continue to Lesson 5

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