CCNA Switching and Network Access Practice Test 11 — 15 Questions

Question 1

A switch port connected to a user PC is configured as a trunk. The PC cannot communicate normally. What is the best explanation?

Accepted Answer

The port role is wrong because a normal PC-facing switchport should usually be an access port, not a trunk. The best explanation is that the port role is wrong: a PC-facing port should be an access port, not a trunk, because PCs normally send untagged frames and cannot process VLAN tags. Option B is incorrect because EtherChannel is used for link aggregation, not required for a single PC. Option C is wrong because trunk mode does not disable MAC address learning. Option D is irrelevant, as switches do not stop using IP addressing in trunk mode.

Answer

A user PC requires EtherChannel to function

Answer

Trunk mode disables MAC address learning automatically

Answer

Trunk mode forces the switch to stop using IP addressing

Question 2

A switch interface connects to a user PC and should belong only to VLAN 30. Which command assigns that VLAN after the interface is in access mode?

Accepted Answer

switchport access vlan 30. After an interface is placed into access mode, the command used to assign its VLAN is `switchport access vlan 30`. In plain language, this tells the switch which VLAN the endpoint traffic on that access port belongs to. Access mode defines the role of the interface, and the access VLAN command defines the specific VLAN membership for that role.

This distinction matters because some commands change the port’s behavior while others set the VLAN it uses. The correct answer is the one that directly assigns VLAN 30 to the access port rather than modifying a trunk or a native VLAN setting.

Answer

switchport trunk allowed vlan 30

Answer

encapsulation dot1Q 30

Answer

ip helper-address 30

Question 3

An EtherChannel should form using LACP between two switches. One side is configured for LACP active, and the other side is configured for LACP active. What is the expected result if the other link settings also match?

Accepted Answer

The EtherChannel should form if the other interface settings are compatible.. The EtherChannel should form successfully if the underlying link settings are compatible. LACP active/active is a valid combination, as both switches actively negotiate the bundle. However, the channel does not automatically become a routed interface (option C is incorrect because EtherChannel can operate as Layer 2 or Layer 3 depending on configuration, not automatically due to LACP mode). Additionally, VLAN tags are not removed by default from the bundle (option D is incorrect; VLAN tagging is preserved based on the switchport mode and allowed VLAN settings). The key troubleshooting point is to ensure that other interface parameters such as speed, duplex, and VLAN settings match across the member ports.

Answer

The channel fails because both sides must be passive.

Answer

The channel becomes a routed interface automatically.

Answer

All VLAN tags are removed from the bundle by default.

Question 4

Two switches are connected by a trunk. VLAN 50 exists on both switches, but traffic still fails across the link. The allowed VLAN list is correct. Which additional item should be checked next?

Accepted Answer

Check for a trunk mismatch such as native VLAN inconsistency or other trunk-parameter problems.. After confirming that the VLAN exists on both switches and is allowed on the trunk, another important item to verify is whether the trunk itself is actually operational with the expected encapsulation and whether there is a native VLAN or other trunk inconsistency. In plain language, just because the VLAN is listed does not guarantee the trunk is healthy in every relevant way. Trunking problems can still occur because of broader configuration mismatches.

This question is about disciplined troubleshooting. Once the obvious allowed-list issue is ruled out, the next step is to keep checking other trunk-related characteristics rather than jumping immediately to unrelated routing or service features. The correct answer is the one that stays grounded in trunk-specific verification.

Answer

Reset OSPF process IDs on both switches.

Answer

Add ip helper-address under every access interface.

Answer

Disable the MAC address table.

Question 5

A switchport connected to another switch is configured with `switchport mode dynamic auto` on both ends. What is the most likely outcome if neither side actively negotiates trunking?

Accepted Answer

The link is likely to remain non-trunking because both sides are waiting passively.. If both ends are set to dynamic auto, the most likely outcome is that the link does not become a trunk automatically. In plain language, both interfaces are waiting passively for the other side to initiate the negotiation. Since neither side is actively trying to form the trunk, the link typically remains non-trunking unless one side is changed to a more active mode or trunk is configured directly.

This is a classic DTP behavior question because it tests whether you understand the difference between active and passive negotiation roles. The correct answer is the one that reflects the passive nature of dynamic auto on both sides.

Answer

The link always becomes a trunk immediately.

Answer

The link becomes a routed Layer 3 link.

Answer

All VLANs are deleted from both switches.

Question 6

Two switches should form an LACP EtherChannel. One side is configured passive, and the other side is also passive. What is the most likely result?

Accepted Answer

The EtherChannel is unlikely to form because neither side initiates LACP negotiation.. If both sides are passive, the EtherChannel is unlikely to form because passive mode waits for the other side to initiate LACP negotiation. In plain language, both switches are listening, but neither is actively starting the conversation. Because neither side takes the active role, the bundle normally stays down or unformed unless one side is changed to active.

This is a classic LACP negotiation question. It reinforces the difference between valid pairings such as active/active or active/passive and the passive/passive pairing that usually fails to initiate negotiation.

Answer

The EtherChannel always forms because passive mode is stronger than active mode.

Answer

The link becomes a routed port automatically.

Answer

Both switches delete the port-channel configuration.

Question 7

A switch port connected to an end host should forward traffic for one VLAN only and should not negotiate trunking. Which configuration approach best fits that requirement?

Accepted Answer

Configure the interface with `switchport mode access`. The best approach is to configure the interface as an access port. In plain language, this tells the switch that the interface is for a normal endpoint and should belong to one VLAN rather than carry multiple VLANs like a trunk. It also avoids reliance on dynamic trunk negotiation, which is usually unnecessary and potentially confusing for a user-facing connection.

This is a standard access-layer design principle. End hosts such as PCs and printers usually connect to access ports, not trunks. That is why the correct answer is the one centered on explicit access-port behavior.

Answer

Configure the interface with `switchport mode trunk`

Answer

Configure the interface with `switchport mode dynamic desirable`

Answer

Configure the interface with `no switchport`

Question 8

An administrator wants a switchport connected to an end device to move to forwarding quickly but does not want that setting used on inter-switch links. Which feature is intended for that edge-port behavior?

Accepted Answer

PortFast. PortFast is intended for that exact edge-port behavior: it allows a host-facing access port to skip the usual listening and learning delays and transition directly to forwarding, enabling end devices to come online quickly. Root guard is used to protect the root bridge election by restricting which ports can become root ports; it is not designed for edge ports. Loop guard prevents alternate or root ports from becoming designated in the absence of BPDUs, which is a different STP protection mechanism. UDLD aggressive mode detects and disables unidirectional links on point-to-point links, typically between switches, not for end-device connections. Therefore, only PortFast meets the requirement for fast forwarding on an edge port without affecting inter-switch links.

Answer

Root guard

Answer

Loop guard

Answer

UDLD aggressive

Question 9

A switch trunk must carry VLANs 10, 20, and 30, but traffic for VLAN 20 is failing. The trunk allowed list on one side is `10,30`. What is the most likely cause?

Accepted Answer

VLAN 20 is missing from the allowed VLAN list on one side of the trunk.. The most likely cause is that VLAN 20 is not in the allowed VLAN list on one side of the trunk. Option B is incorrect because converting the trunk to an access port would block all other VLANs, not just fix VLAN 20. Option C is incorrect because there is no requirement that VLAN 20 must be the native VLAN; native VLAN is unrelated to allowed list filtration. Option D is incorrect because ISL vs 802.1Q does not affect per-VLAN filtering; the allowed list is a separate configuration independent of the encapsulation type.

Answer

The trunk must be converted to an access port for VLAN 20 to work.

Answer

VLAN 20 must always be the native VLAN.

Answer

The switches must both use ISL instead of 802.1Q.

Question 10

A switch port connected to an end host is configured with both PortFast and BPDU Guard. What is the most likely outcome if a small switch is connected there and starts sending BPDUs?

Accepted Answer

The port is error-disabled by BPDU Guard.. BPDU Guard places the port into an error-disabled state upon receiving a BPDU, because PortFast defines the port as an edge port that should never receive BPDUs. Option B is incorrect because receiving a BPDU does not automatically make a port a root port; root port selection depends on bridge ID and path cost, and BPDU Guard prevents further STP processing by disabling the port. Option C is incorrect because a port cannot convert to a trunk solely by receiving a BPDU; trunking requires manual configuration or Dynamic Trunking Protocol (DTP). Option D is incorrect because PortFast does not disable STP entirely; it only speeds up initial convergence, and BPDU Guard actively responds to BPDUs by error-disabling the port.

Answer

The port automatically becomes the root port.

Answer

The port converts into a trunk for the attached switch.

Answer

The port ignores the BPDU because PortFast disables STP entirely.

Question 11

Two switches should form an EtherChannel using LACP. One side is configured active and the other passive. If the port settings otherwise match, what is the expected result?

Accepted Answer

The EtherChannel should form if the other interface settings are compatible.. The EtherChannel should form successfully. In plain language, active mode initiates LACP negotiation and passive mode listens and responds. Because one side is active, the negotiation can begin and the bundle can come up as long as the underlying interface settings are compatible.

This is a standard LACP pairing. The important lesson is that active/passive works, while passive/passive usually does not. The correct answer is the one that recognizes active/passive as a valid combination.

Answer

The EtherChannel fails because both sides must be active.

Answer

the bundle forms but only in PAgP mode

Answer

only the active side attempts to bundle

Question 12

A switchport connected to another switch should carry VLANs 10, 20, and 30. The interface is operational, but only VLAN 10 works. VLANs 20 and 30 fail. Which explanation is most likely if the port was accidentally configured as an access port in VLAN 10?

Accepted Answer

The interface is carrying only VLAN 10 because an access port does not transport multiple VLANs like a trunk.. An access port is limited to a single VLAN, so only VLAN 10 traverses the link. Option B is incorrect: IP subnet masks are irrelevant on switchports that operate at Layer 2. Option C is incorrect: inter-switch links typically use trunk ports, not routed ports. Option D is incorrect: STP does not block based on VLAN IDs; it blocks redundant paths, not specific VLANs.

Answer

VLAN 20 and 30 require different IP subnet masks on the switches.

Answer

Every inter-switch link must use a routed port instead of a trunk.

Answer

STP blocks all VLANs except VLAN 10 by design.

Question 13

A switchport is configured as a trunk on one side and access on the other side of the same physical link. What is the most likely result?

Accepted Answer

The link roles are mismatched, so VLAN traffic will not be handled as intended across the link.. A trunk/access mismatch prevents the link from carrying VLAN traffic as intended. Option A correctly identifies this mismatch. Option B is wrong because access ports remain Layer 2 switchports; there is no automatic conversion to a routed port. Option C fails because switch configurations are never auto-synchronized due to a port role mismatch. Option D is incorrect: OSPF router ID is chosen based on loopback or highest IP address and is unaffected by a Layer 2 port mismatch.

Answer

The access side automatically becomes a routed port.

Answer

The switches automatically synchronize their configurations.

Answer

The mismatch forces OSPF to choose a new router ID.

Question 14

PCs in VLAN 30 on SwitchA cannot reach PCs in VLAN 30 on SwitchB. VLAN 30 exists on both switches and all other VLANs work across the same link. Based on the exhibit, what is the most likely cause?

Accepted Answer

VLAN 30 is not allowed on the trunk from SwitchA.. The trunk is up, but VLAN 30 is missing from the allowed list on SwitchA. In plain language, the hallway between the switches is open, but one side is refusing to carry that specific VLAN through the hallway. Since the other VLANs are working, the failure is selective rather than total. That strongly points to an allowed-VLAN problem rather than a broader trunk outage.

This is a classic CCNA switching scenario because it tests whether you can separate trunk health from per-VLAN forwarding. A trunk can be operational and still block one VLAN if that VLAN is not permitted on one side. The native VLAN and encapsulation are not the issue shown here — the mismatch in the allowed list is.

Answer

The native VLAN is mismatched.

Answer

The trunk must use ISL instead of 802.1Q.

Answer

VLAN 30 must be configured as the native VLAN.

Question 15

A port connected to an end host is configured with PortFast and BPDU Guard. What is the most likely result if a small unmanaged switch is connected and starts sending BPDUs?

Accepted Answer

The port is error-disabled by BPDU Guard.. The most likely result is that the port is placed into an err-disabled state by BPDU Guard. In practical terms, PortFast tells the switch to treat the interface like an edge port for a normal endpoint, which is why it starts forwarding quickly. BPDU Guard protects that assumption. If the port suddenly receives a spanning-tree BPDU, the switch treats that as a sign that the port is no longer connected to a simple end device.

This combination is common in enterprise access-layer design because it improves user startup time while still protecting the topology. The correct answer is the one that describes the port being shut down automatically when BPDUs appear unexpectedly.

Answer

The port automatically becomes the root port.

Answer

The port is converted into a trunk.

Answer

The port ignores the BPDU because PortFast disables STP entirely.