Cisco CCNA VLANs and 802.1Q Trunking 2 — Questions and Answers
Question 1: What is the valid VLAN ID range for extended VLANs on a Cisco switch?
- 1006–4094 (Correct answer)
- 1025–4094
- 1006–4095
- 1024–4096
Correct answer: 1006–4094
Extended VLANs use IDs 1006–4094, while normal-range VLANs span 1–1005.
Question 2: Which command verifies the trunking status and allowed VLANs on interface Gi0/1?
- show interfaces Gi0/1 trunk (Correct answer)
- show vlan brief
- show interfaces Gi0/1 switchport
- show trunk Gi0/1
Correct answer: show interfaces Gi0/1 trunk
`show interfaces Gi0/1 trunk` displays trunking mode, encapsulation, and the allowed VLAN list.
Question 3: A port is configured with `switchport mode dynamic desirable`. What will happen if the neighboring port is set to `switchport mode access`?
- The port becomes an access port (Correct answer)
- The port becomes a trunk
- The link goes down
- The port stays in dynamic desirable mode indefinitely
Correct answer: The port becomes an access port
Dynamic desirable will form a trunk only if the neighbor also negotiates trunking; an access-mode neighbor causes it to become an access port.
Question 4: Which 802.1Q field identifies the VLAN to which a frame belongs?
- VLAN ID (VID) (Correct answer)
- Priority Code Point (PCP)
- Drop Eligible Indicator (DEI)
- EtherType (0x8100)
Correct answer: VLAN ID (VID)
The 12-bit VLAN Identifier (VID) field in the 802.1Q tag specifies the VLAN.
Question 5: What happens to traffic from a VLAN that has been pruned from a trunk link?
- It is not forwarded across that trunk (Correct answer)
- It is forwarded as untagged traffic
- It is dropped and logged
- It is redirected to the native VLAN
Correct answer: It is not forwarded across that trunk
VTP pruning or manual pruning removes a VLAN from a trunk so its traffic is not flooded unnecessarily across that link.
Question 6: A switch receives a tagged frame with VLAN 10 on a port configured as an access port for VLAN 20. What does the switch do?
- Drops the frame (Correct answer)
- Forwards the frame to VLAN 10
- Strips the tag and forwards on VLAN 20
- Adds a second tag and floods the frame
Correct answer: Drops the frame
Cisco switches drop tagged frames received on access ports because access ports expect untagged traffic.
Question 7: What is the purpose of the `switchport trunk native vlan 99` command?
- Sets VLAN 99 as the untagged VLAN on the trunk (Correct answer)
- Allows only VLAN 99 on the trunk
- Makes VLAN 99 the management VLAN
- Removes all other VLANs from the trunk
Correct answer: Sets VLAN 99 as the untagged VLAN on the trunk
This command changes the native VLAN on the trunk to VLAN 99, so untagged frames are associated with VLAN 99.
Cisco CCNA VLANs and 802.1Q Trunking 2
What is the valid VLAN ID range for extended VLANs on a Cisco switch?