Cisco CCNA VLANs and 802.1Q Trunking 5 — Questions and Answers
Question 1: Which command is used to verify which VLANs are forwarding on a specific trunk interface?
- show interfaces trunk (Correct answer)
- show spanning-tree vlan
- show vlan id
- show interfaces status
Correct answer: show interfaces trunk
`show interfaces trunk` shows active VLANs in STP forwarding state on each trunk port.
Question 2: A voice VLAN is configured on an access port with `switchport voice vlan 50`. How does the switch handle voice traffic on that port?
- Voice traffic is tagged with VLAN 50 and data traffic remains untagged on the access VLAN (Correct answer)
- All traffic is tagged with VLAN 50
- Voice traffic is untagged and data traffic uses VLAN 50
- The port becomes a trunk and carries both VLANs tagged
Correct answer: Voice traffic is tagged with VLAN 50 and data traffic remains untagged on the access VLAN
With a voice VLAN configured, the IP phone sends tagged voice frames on VLAN 50 while the PC behind it sends untagged data on the access VLAN.
Question 3: What happens when you delete vlan.dat from the switch's flash memory?
- All normal-range VLAN configurations are erased and reset to defaults (Correct answer)
- Only extended VLANs are removed
- The switch reboots and loses the running configuration
- VLAN 1 is deleted along with all others
Correct answer: All normal-range VLAN configurations are erased and reset to defaults
Deleting vlan.dat removes all normal-range VLAN definitions, resetting the switch to factory VLAN defaults on next boot.
Question 4: Which of the following is a reserved VLAN that cannot be deleted or used for data traffic on Cisco switches?
- VLAN 1002 (Correct answer)
- VLAN 1006
- VLAN 999
- VLAN 100
Correct answer: VLAN 1002
VLANs 1002–1005 are reserved for legacy Token Ring and FDDI protocols and cannot be deleted or modified.
Question 5: On a Layer 3 switch, what is required for inter-VLAN routing using Switched Virtual Interfaces (SVIs)?
- An SVI must be created for each VLAN and IP routing must be enabled (Correct answer)
- A router-on-a-stick subinterface must be configured
- VLANs must be connected via a Layer 2 trunk to a router
- Each VLAN must have a dedicated physical routed port
Correct answer: An SVI must be created for each VLAN and IP routing must be enabled
Inter-VLAN routing via SVIs requires creating a VLAN interface (SVI) for each VLAN and enabling `ip routing` on the Layer 3 switch.
Question 6: What is the result of configuring mismatched native VLANs on opposite ends of an 802.1Q trunk?
- CDP/STP generates a native VLAN mismatch error and traffic may be misrouted (Correct answer)
- The trunk goes down immediately
- Traffic is forwarded normally with no impact
- The switch automatically corrects the mismatch using VTP
Correct answer: CDP/STP generates a native VLAN mismatch error and traffic may be misrouted
A native VLAN mismatch causes CDP and STP to generate warnings, and untagged frames can be placed into the wrong VLAN, causing a security and connectivity issue.
Question 7: Which command enables 802.1Q trunking on a Catalyst switch interface and statically sets the encapsulation?
- switchport trunk encapsulation dot1q (Correct answer)
- switchport mode trunk dot1q
- encapsulation dot1q trunk
- trunk encapsulation 802.1q
Correct answer: switchport trunk encapsulation dot1q
On switches that support both ISL and 802.1Q, `switchport trunk encapsulation dot1q` must be issued before enabling trunk mode.
Cisco CCNA VLANs and 802.1Q Trunking 5
Which command is used to verify which VLANs are forwarding on a specific trunk interface?