CCNA Switching and Network Access Practice Test 8 — 15 Questions

Question 1

Which TWO statements are true regarding switch port configuration for access, voice, and trunk ports?

Accepted Answer

A switch port configured as a trunk port can simultaneously carry untagged traffic for the native VLAN and tagged traffic for multiple other VLANs.. A trunk port, by definition, carries untagged frames for the native VLAN (typically VLAN 1 unless changed) and simultaneously carries tagged frames for all other VLANs allowed on the trunk. This behavior is fundamental to IEEE 802.1Q trunking, where the native VLAN is the only VLAN whose frames are sent untagged to maintain backward compatibility with devices that do not understand VLAN tagging. For voice deployments, an access port can be configured with both an access VLAN (for data devices) and a voice VLAN (for IP phones). When an IP phone is connected, the switch uses CDP (or LLDP-MED) to advertise the voice VLAN ID to the phone, allowing the phone to tag its voice traffic with that VLAN while data traffic from a connected PC remains untagged in the access VLAN. Therefore, statement D is also true.

Answer

When a port is configured with both an access VLAN and a voice VLAN, the switchport must be set to trunk mode.

Answer

The switchport mode dynamic auto command sets the port to actively attempt to form a trunk if the neighbor initiates negotiation.

Answer

Issuing the switchport trunk allowed vlan command automatically includes the native VLAN in the allowed list, so it never needs to be explicitly added.

Question 2

Which THREE statements about STP and Rapid PVST+ are correct?

Accepted Answer

Rapid PVST+ creates a separate spanning-tree instance for each VLAN, enabling per-VLAN load balancing.. Rapid PVST+ is Cisco's per-VLAN implementation of RSTP (802.1w). It creates a separate spanning-tree instance for each VLAN, allowing independent convergence and per-VLAN load balancing by blocking different ports in different VLANs (A). Rapid PVST+ uses the RSTP proposal/agreement handshake to transition designated and root ports to forwarding quickly without relying on timers (C). BPDU Guard is a security feature that, when enabled on a port (typically a PortFast edge port), places the port in error-disabled state if it receives a BPDU, preventing loops from unexpected switches (D).

Answer

PortFast should be configured on trunk ports to quickly transition them to forwarding state.

Answer

To make a switch the root bridge, you should assign it the highest bridge priority value among all switches.

Question 3

A network engineer connects a new switch to an existing Rapid PVST+ campus network. The new switch is intended to serve as an additional access-layer switch, but after connecting its uplinks, the engineer discovers that the root bridge for VLAN 10 has changed to this new switch, and several access ports on other switches with PortFast and BPDU Guard enabled are now in err-disabled state. Some users report intermittent connectivity loss.

Accepted Answer

The new switch’s bridge priority is lower than the existing root bridge, and it was connected to a port with BPDU Guard enabled.. The new switch has a lower bridge priority, so it becomes the root bridge for VLAN 10, changing the root. As the new root, it sends BPDUs out its designated ports. Any PortFast port with BPDU Guard enabled that receives an unexpected BPDU (even from a legitimate switch) will be placed into err-disabled state. This explains the err-disabled access ports and connectivity loss.

Answer

The new switch was connected to a port configured as a trunk with a native VLAN mismatch.

Answer

The new switch has PortFast enabled on its uplinks.

Answer

The BPDU Guard feature was globally enabled on all ports, including trunk ports.

Question 4

Which TWO statements accurately describe 802.1Q trunking and inter-VLAN routing on Cisco switches?

Accepted Answer

802.1Q trunking adds a 4-byte tag that includes a 12-bit VLAN ID field, increasing the maximum frame size.. 802.1Q trunking inserts a 4-byte tag into the Ethernet frame, which includes a 12-bit VLAN ID field (supporting up to 4094 usable VLANs). This tag increases the maximum frame size from 1518 bytes to 1522 bytes, a key characteristic of 802.1Q encapsulation. Router-on-a-stick inter-VLAN routing is achieved by configuring subinterfaces on a single physical router interface. Each subinterface is assigned an 802.1Q encapsulation for a specific VLAN and an IP address from a unique subnet corresponding to that VLAN, allowing the router to route between VLANs.

Answer

The native VLAN on a trunk port sends frames with an 802.1Q tag containing VLAN ID 1.

Answer

A trunk port can only forward traffic for one VLAN at a time.

Answer

The native VLAN on a trunk cannot be changed from VLAN 1.

Question 5

Refer to the exhibit. A network administrator is troubleshooting a connectivity issue on switch SW1. Users connected to port Gi0/3 are unable to reach resources in VLAN 30. The administrator issues the show vlan brief command and receives the output shown. What is the most likely cause of the problem?

Accepted Answer

VLAN 30 is administratively shut down.. The 'show vlan brief' output shows VLAN 30 with a status of 'act/lshut' (administratively shutdown) or 'shutdown', indicating that the VLAN has been disabled via the 'shutdown' command in VLAN configuration mode. A shutdown VLAN does not forward traffic, and all access ports assigned to it become operationally inactive for that VLAN, even though the ports themselves may still be listed in the output. The SVI for VLAN 30 would also be down. Therefore, the most likely cause is that VLAN 30 has been administratively shut down.

Answer

The Gi0/3 port is in an error-disabled state due to port security violations.

Answer

The VLAN 30 SVI is administratively down.

Answer

Spanning Tree Protocol has placed Gi0/3 into a blocking state for VLAN 30.

Question 6

A technician connects a PC to a switch port that has port security enabled with the default maximum of one MAC address and violation mode shutdown. Immediately after connecting, the port goes into the err-disabled state. The technician runs the show interfaces command and sees the port status as err-disabled. What should the technician do next?

Accepted Answer

Configure the port security violation mode to restrict, increase the maximum number of MAC addresses, and then recover the port.. The port entered err-disabled due to a port security violation (the PC's MAC differs from the allowed secure MAC, exceeding the default maximum of 1). Simply recovering the port with shutdown/no shutdown would not fix the underlying problem, as any traffic from the PC would immediately trigger another violation. The technician should first adjust the port security configuration to accommodate the PC: configure the violation mode to restrict (which drops packets from unknown MACs but keeps the port up and logs events) and increase the maximum number of MAC addresses to allow the PC's MAC to be learned. Then recover the port using shutdown/no shutdown (or errdisable recovery). Option A describes this correct approach.

Answer

Disable port security on the interface.

Answer

Enter the shutdown and no shutdown commands to recover the port, then enable port security with sticky MAC learning.

Answer

Verify the spanning-tree portfast configuration on the interface.

Question 7

Refer to the exhibit. A network engineer configured an EtherChannel between SW1 and SW2 using LACP. After the configuration is applied, the Port-channel 1 interface remains in a down state and does not pass traffic. The engineer runs the show etherchannel detail command on SW1. Based on the output, what is the most likely cause of the problem?

Accepted Answer

The interface Gi0/1 is administratively down.. An EtherChannel requires all member ports to have consistent VLAN configurations. However, if one port (Gi0/2) has a native VLAN mismatch, only that port is suspended/excluded from the channel. The port-channel can still become active using other valid members. In this scenario, the port-channel remains down because Gi0/1 is administratively down, leaving no valid member ports to form the channel. The show etherchannel detail output would indicate Gi0/1 in an administratively down state and Gi0/2 in a suspended state due to the native VLAN mismatch.

Answer

The native VLAN is mismatched on member interface Gi0/2.

Answer

The load-balancing method on the port-channel is set incorrectly to src-dst-ip.

Answer

Spanning Tree Protocol has placed the port-channel in a blocking state due to a loop.

Question 8

Refer to the exhibit. A network engineer notices packet loss and sluggish application performance on a branch-office uplink. While troubleshooting, the engineer executes the show interfaces GigabitEthernet0/1 command on the router. Based on the output, what is the most likely cause of the performance issue?

Accepted Answer

An upstream device is sending traffic at a rate higher than this interface can transmit, causing the output queue to overflow.. The interface shows a high number of output drops, indicating that the output queue is experiencing congestion and packets are being dropped because the router cannot transmit traffic as fast as it is being received from the upstream device. This causes packet loss and sluggish performance.

Answer

The interface is experiencing excessive collisions due to a duplex mismatch.

Answer

The interface is receiving corrupted frames, indicated by the zero input errors on the interface.

Answer

The output queue is full because its size is too small, and increasing the queue depth will resolve the packet loss.

Question 9

Which spanning-tree port state listens for BPDUs and participates in STP, but does not learn MAC addresses yet?

Accepted Answer

Listening. In the classic 802.1D sequence, the listening state processes BPDUs and prepares for forwarding decisions, but it does not populate the MAC address table yet.

Answer

Blocking

Answer

Learning

Answer

Forwarding

Question 10

What is a common requirement for interfaces to successfully bundle into an EtherChannel?

Accepted Answer

All member interfaces must use matching speed, duplex, and trunk/access settings. EtherChannel members must have compatible operational and administrative settings, including speed, duplex, and switchport mode.

Answer

Each interface must belong to a different VLAN

Answer

Only odd-numbered switch ports can be bundled

Answer

Each interface must have a different STP path cost

Question 11

In a router-on-a-stick design, what is configured on the physical router interface connected to the switch?

Accepted Answer

Subinterfaces with 802.1Q encapsulation for each routed VLAN. Router-on-a-stick uses one physical router interface with multiple logical subinterfaces. Each subinterface is associated with a VLAN using 802.1Q encapsulation and gets an IP address for that VLAN. Option A is wrong because IP addresses are configured on subinterfaces, not directly on the physical interface for all VLANs. Option B is wrong because inter-VLAN routing requires a router; the switch alone does not perform inter-VLAN routing in this design. Option D is wrong because serial encapsulation is used for WAN connections, not for VLAN tagging on Ethernet interfaces.

Answer

One IP address for every VLAN on the physical interface itself only

Answer

No subinterfaces; the switch handles all inter-VLAN routing internally

Answer

A serial encapsulation setting for each VLAN

Question 12

A switch receives a unicast frame for a destination MAC address that is not yet in its MAC address table. What does the switch do?

Accepted Answer

Floods the frame out all ports in the same VLAN except the incoming port. An unknown unicast frame is flooded within the VLAN because the switch does not yet know which port leads to the destination MAC. The frame is not sent back out the receiving port.

Answer

Drops the frame immediately

Answer

Sends the frame to the default gateway first

Answer

Converts the frame to a broadcast packet

Question 13

When spanning tree elects a root bridge, which value is considered first?

Accepted Answer

Lowest bridge ID, which begins with priority. The root bridge is the switch with the lowest bridge ID. The bridge ID is made up of priority and MAC address, so priority is considered first, then MAC address if priorities tie.

Answer

Lowest MAC address only

Answer

Lowest bridge priority only

Answer

Highest interface bandwidth

Question 14

What problem does Spanning Tree Protocol solve in a switched network?

Accepted Answer

Layer 2 switching loops. STP prevents Layer 2 loops by blocking redundant paths when necessary, which avoids broadcast storms and MAC table instability.

Answer

IP address exhaustion

Answer

Slow DNS lookups

Answer

Weak wireless encryption

Question 15

Hosts in VLAN 10 need to communicate with hosts in VLAN 20. What is required for that communication to work?

Accepted Answer

A Layer 3 routing function. Traffic between VLANs must be routed. A router or multilayer switch provides the Layer 3 function needed for inter-VLAN communication.

Answer

A DHCP server

Answer

A DNS server

Answer

A second access switch