Cisco CCNA Network Access Certification Exam | Complete
Practice Test, Verified Answers & Expert Explanations
2026/2027
Question 1
What is the primary operational benefit of implementing Virtual Local
Area Networks (VLANs) in an enterprise switched network?
A. They increase the physical bandwidth of copper cables automatically.
B. They logically segment broadcast domains at Layer 2, improving
security and reducing unnecessary broadcast traffic.
C. They replace the requirement for a default gateway router entirely.
D. They encrypt all user data passing across switches.
Correct Answer: B. They logically segment broadcast domains at Layer
2, improving security and reducing unnecessary broadcast traffic.
Detailed Rationale: VLANs allow a network administrator to break up a
single physical switch chassis into multiple isolated broadcast domains,
containing broadcast traffic and enhancing organizational security.
Question 2
How does the IEEE 802.1Q standard identify which VLAN a particular
Ethernet frame belongs to when traversing a trunk link?
A. By modifying the source MAC address bits.
,B. By inserting a 4-byte VLAN tag directly into the Ethernet frame
header between the Source MAC address and the EtherType/Length
field.
C. By converting the packet into an IPv6 header option.
D. By appending an FCS trailer at the end of the frame.
Correct Answer: B. By inserting a 4-byte VLAN tag directly into the
Ethernet frame header between the Source MAC address and the
EtherType/Length field.
Detailed Rationale: The 802.1Q tag consists of a Tag Protocol Identifier
(TPID) and a Tag Control Information (TCI) field containing the 12-bit
VLAN ID.
Question 3
What happens to an untagged frame when it arrives at an 802.1Q trunk
port on a Cisco Catalyst switch?
A. It is dropped immediately for security violations.
B. It is assumed to belong to the configured Native VLAN and is
processed accordingly.
C. It is converted into a broadcast packet and flooded out all ports.
D. It is sent directly to the CPU for manual inspection.
Correct Answer: B. It is assumed to belong to the configured Native
VLAN and is processed accordingly.
Question 4
,When a Cisco switch port is configured with switchport mode dynamic
desirable, how does it interact with a neighboring switch port set to
dynamic auto using Dynamic Trunking Protocol (DTP)?
A. A trunk link is successfully formed.
B. Both ports remain in access mode because neither initiates the
negotiation.
C. The ports enter an error-disabled state due to a DTP mismatch.
D. The link switches to a half-duplex hub mode.
Correct Answer: A. A trunk link is successfully formed.
Detailed Rationale: DTP requires at least one side to be proactive
(desirable or trunk). When one side is desirable and the other is auto,
the link successfully negotiates and forms an 802.1Q trunk.
Question 5
In Spanning Tree Protocol (STP), which parameter determines which
switch is elected as the Root Bridge?
A. The highest MAC address on the switch chassis.
B. The lowest Bridge ID, which is a combination of the configurable
Bridge Priority and the switch MAC address.
C. The highest port count available on the switch.
D. The physical location closest to the core router.
Correct Answer: B. The lowest Bridge ID, which is a combination of the
configurable Bridge Priority and the switch MAC address.
Question 6
, What is the primary function of the Spanning Tree Protocol (STP)?
A. To increase network routing speed across WAN links.
B. To prevent Layer 2 switching loops by dynamically blocking
redundant physical paths while maintaining network fault tolerance.
C. To balance traffic loads evenly across all available switch ports.
D. To assign IP addresses to dynamic hosts.
Correct Answer: B. To prevent Layer 2 switching loops by dynamically
blocking redundant physical paths while maintaining network fault
tolerance.
Question 7
What is the primary purpose of enabling PortFast on an access switch
port connected to an end-user workstation?
A. It increases the port speed to 10 Gbps.
B. It bypasses the STP Listening and Learning states, allowing the port to
transition immediately to the Forwarding state to prevent client DHCP
timeouts.
C. It encrypts all traffic leaving the workstation.
D. It disables Spanning Tree Protocol across the entire switch chassis.
Correct Answer: B. It bypasses the STP Listening and Learning states,
allowing the port to transition immediately to the Forwarding state to
prevent client DHCP timeouts.
Question 8
Practice Test, Verified Answers & Expert Explanations
2026/2027
Question 1
What is the primary operational benefit of implementing Virtual Local
Area Networks (VLANs) in an enterprise switched network?
A. They increase the physical bandwidth of copper cables automatically.
B. They logically segment broadcast domains at Layer 2, improving
security and reducing unnecessary broadcast traffic.
C. They replace the requirement for a default gateway router entirely.
D. They encrypt all user data passing across switches.
Correct Answer: B. They logically segment broadcast domains at Layer
2, improving security and reducing unnecessary broadcast traffic.
Detailed Rationale: VLANs allow a network administrator to break up a
single physical switch chassis into multiple isolated broadcast domains,
containing broadcast traffic and enhancing organizational security.
Question 2
How does the IEEE 802.1Q standard identify which VLAN a particular
Ethernet frame belongs to when traversing a trunk link?
A. By modifying the source MAC address bits.
,B. By inserting a 4-byte VLAN tag directly into the Ethernet frame
header between the Source MAC address and the EtherType/Length
field.
C. By converting the packet into an IPv6 header option.
D. By appending an FCS trailer at the end of the frame.
Correct Answer: B. By inserting a 4-byte VLAN tag directly into the
Ethernet frame header between the Source MAC address and the
EtherType/Length field.
Detailed Rationale: The 802.1Q tag consists of a Tag Protocol Identifier
(TPID) and a Tag Control Information (TCI) field containing the 12-bit
VLAN ID.
Question 3
What happens to an untagged frame when it arrives at an 802.1Q trunk
port on a Cisco Catalyst switch?
A. It is dropped immediately for security violations.
B. It is assumed to belong to the configured Native VLAN and is
processed accordingly.
C. It is converted into a broadcast packet and flooded out all ports.
D. It is sent directly to the CPU for manual inspection.
Correct Answer: B. It is assumed to belong to the configured Native
VLAN and is processed accordingly.
Question 4
,When a Cisco switch port is configured with switchport mode dynamic
desirable, how does it interact with a neighboring switch port set to
dynamic auto using Dynamic Trunking Protocol (DTP)?
A. A trunk link is successfully formed.
B. Both ports remain in access mode because neither initiates the
negotiation.
C. The ports enter an error-disabled state due to a DTP mismatch.
D. The link switches to a half-duplex hub mode.
Correct Answer: A. A trunk link is successfully formed.
Detailed Rationale: DTP requires at least one side to be proactive
(desirable or trunk). When one side is desirable and the other is auto,
the link successfully negotiates and forms an 802.1Q trunk.
Question 5
In Spanning Tree Protocol (STP), which parameter determines which
switch is elected as the Root Bridge?
A. The highest MAC address on the switch chassis.
B. The lowest Bridge ID, which is a combination of the configurable
Bridge Priority and the switch MAC address.
C. The highest port count available on the switch.
D. The physical location closest to the core router.
Correct Answer: B. The lowest Bridge ID, which is a combination of the
configurable Bridge Priority and the switch MAC address.
Question 6
, What is the primary function of the Spanning Tree Protocol (STP)?
A. To increase network routing speed across WAN links.
B. To prevent Layer 2 switching loops by dynamically blocking
redundant physical paths while maintaining network fault tolerance.
C. To balance traffic loads evenly across all available switch ports.
D. To assign IP addresses to dynamic hosts.
Correct Answer: B. To prevent Layer 2 switching loops by dynamically
blocking redundant physical paths while maintaining network fault
tolerance.
Question 7
What is the primary purpose of enabling PortFast on an access switch
port connected to an end-user workstation?
A. It increases the port speed to 10 Gbps.
B. It bypasses the STP Listening and Learning states, allowing the port to
transition immediately to the Forwarding state to prevent client DHCP
timeouts.
C. It encrypts all traffic leaving the workstation.
D. It disables Spanning Tree Protocol across the entire switch chassis.
Correct Answer: B. It bypasses the STP Listening and Learning states,
allowing the port to transition immediately to the Forwarding state to
prevent client DHCP timeouts.
Question 8
