ICND1 VLAN Management 4 — Questions and Answers
Question 1: A switch has VTP revision number 100. A new switch with revision number 150 is connected. What is the likely outcome?
- The new switch adopts the existing domain's VLAN database
- The new switch overwrites the domain's VLAN database with its higher revision (Correct answer)
- VTP negotiates a merged VLAN database
- Both switches reset their revision numbers to 0
Correct answer: The new switch overwrites the domain's VLAN database with its higher revision
VTP always synchronizes to the highest revision number, so the new switch's database overwrites the domain's existing VLAN configuration—a common accidental outage scenario.
Question 2: Which command changes the native VLAN of a trunk to VLAN 99?
- switchport trunk native vlan 99 (Correct answer)
- switchport native vlan 99
- vlan 99 native
- switchport trunk vlan native 99
Correct answer: switchport trunk native vlan 99
'switchport trunk native vlan 99' sets the native VLAN for untagged traffic on an 802.1Q trunk to VLAN 99.
Question 3: What is a voice VLAN on a Cisco switch access port?
- A separate VLAN that carries only SIP signaling traffic
- A second VLAN on an access port that tags voice traffic for IP phones (Correct answer)
- A trunk subinterface dedicated to VoIP
- A VLAN restricted to multicast packets
Correct answer: A second VLAN on an access port that tags voice traffic for IP phones
A voice VLAN enables an access port to carry two VLANs: one untagged for the PC and one tagged (voice VLAN) for the IP phone connected to the same port.
Question 4: An administrator wants to see which VLANs are currently active and forwarding on trunk interface Gi0/1. Which command helps?
- show interfaces gi0/1 trunk (Correct answer)
- show vlan brief
- show spanning-tree vlan
- show trunk interfaces
Correct answer: show interfaces gi0/1 trunk
'show interfaces gi0/1 trunk' displays the VLANs allowed, active, and forwarding on that specific trunk port.
Question 5: Inter-VLAN routing using a 'router-on-a-stick' configuration requires which interface type on the router?
- Physical interfaces — one per VLAN
- Loopback interfaces
- Subinterfaces with 802.1Q encapsulation (Correct answer)
- Tunnel interfaces
Correct answer: Subinterfaces with 802.1Q encapsulation
Router-on-a-stick uses a single physical interface divided into logical subinterfaces, each configured with 'encapsulation dot1q <vlan-id>' to route between VLANs.
Question 6: Which statement correctly describes extended-range VLANs (1006–4094)?
- They are supported only in VTP server mode
- They require VTP version 3 or transparent mode to be propagated/stored (Correct answer)
- They are automatically pruned by VTP
- They cannot be used with 802.1Q trunks
Correct answer: They require VTP version 3 or transparent mode to be propagated/stored
Extended-range VLANs (1006–4094) are stored in running-config rather than vlan.dat and require VTP version 3 or VTP transparent mode for proper operation.
Question 7: What does the command 'switchport trunk allowed vlan add 40' accomplish?
- Replaces the allowed list with only VLAN 40
- Appends VLAN 40 to the existing list of allowed trunk VLANs (Correct answer)
- Removes VLAN 40 from the allowed list
- Sets VLAN 40 as the native VLAN
Correct answer: Appends VLAN 40 to the existing list of allowed trunk VLANs
The 'add' keyword appends the specified VLAN to the current allowed list without removing any previously permitted VLANs.
ICND1 VLAN Management 4
A switch has VTP revision number 100.
A new switch with revision number 150 is connected.
What is the likely outcome?