Cisco ENCOR Lan Switches 3 — Questions and Answers
Question 1: Which VLAN is used as the native VLAN on a Cisco trunk by default and receives untagged 802.1Q frames?
- VLAN 0
- VLAN 1 (Correct answer)
- VLAN 1002
- VLAN 4094
Correct answer: VLAN 1
VLAN 1 is the default native VLAN on Cisco trunk ports and carries untagged traffic across 802.1Q trunk links.
Question 2: A network administrator wants to prevent rogue DHCP servers on access ports. Which feature should be enabled?
- Dynamic ARP Inspection
- IP Source Guard
- DHCP Snooping (Correct answer)
- Port Security
Correct answer: DHCP Snooping
DHCP Snooping classifies ports as trusted or untrusted and drops DHCP offer/acknowledgment messages arriving on untrusted ports.
Question 3: In Rapid PVST+ (802.1w), which port role replaces the traditional Blocking port in classic STP?
- Alternate port (Correct answer)
- Backup port
- Edge port
- Discarding port
Correct answer: Alternate port
RSTP introduces the Alternate port role, which provides a pre-calculated backup path to the root and can transition quickly when the root port fails.
Question 4: What is the purpose of the BPDU Guard feature on a switch port?
- Prevents the switch from becoming the root bridge
- Shuts down a PortFast-enabled port if it receives a BPDU (Correct answer)
- Filters BPDUs on trunk ports
- Reduces the BPDU hello timer
Correct answer: Shuts down a PortFast-enabled port if it receives a BPDU
BPDU Guard err-disables a PortFast port immediately upon receiving a BPDU, protecting the STP topology from unauthorized switches.
Question 5: Which EtherChannel mode combination between two switches forms a bundle using LACP without sending negotiation frames from one side?
- Active – Active
- Passive – Passive
- Active – Passive (Correct answer)
- Desirable – Auto
Correct answer: Active – Passive
LACP Active mode actively sends negotiation frames while Passive mode responds but does not initiate; at least one side must be Active for the bundle to form.
Question 6: When a switch port is configured with 'switchport mode dynamic desirable', what happens when the neighbor port is set to 'switchport mode access'?
- The link becomes a trunk
- The link remains an access port (Correct answer)
- Negotiation fails and the port is err-disabled
- The port becomes a routed port
Correct answer: The link remains an access port
A port in dynamic desirable mode will attempt to negotiate a trunk, but if the neighbor is statically set to access mode, DTP negotiation fails and the link operates as an access port.
Question 7: Which command verifies the MAC address table entries on a Cisco switch for a specific VLAN?
- show arp vlan <id>
- show mac address-table vlan <id> (Correct answer)
- show interfaces vlan <id>
- show ip interface vlan <id>
Correct answer: show mac address-table vlan <id>
The 'show mac address-table vlan <id>' command displays all CAM table entries associated with the specified VLAN.
Cisco ENCOR Lan Switches 3
Which VLAN is used as the native VLAN on a Cisco trunk by default and receives untagged 802.1Q frames?