CCNA Practice Test 26 — 15 Questions

Question 1

A network technician is troubleshooting connectivity between two directly connected Cisco switches. Hosts on VLAN 10 connected to SwitchA cannot ping the default gateway on SwitchB. The interface on SwitchB shows up/up, but the interface on SwitchA shows up/down. The technician examines the interface configuration and status on SwitchA. What is the most likely cause of this issue?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Configure both interfaces with the same duplex and speed settings, either both auto or both manually set to full-duplex and 1000 Mbps.. The interface on SwitchA shows up/down, meaning Layer 1 is active but the line protocol is down. This is commonly caused by a speed mismatch between the two ends. A duplex mismatch, in contrast, typically results in both interfaces showing up/up with CRC errors. Therefore, the most likely cause is that the speed settings differ—for example, one interface is set to auto-negotiate while the other is hard-coded to a specific speed. Configuring both interfaces with identical speed and duplex settings, either both auto or both manually configured, resolves the issue.

Answer

Replace the Ethernet cable because it is faulty.

Answer

Issue the 'shutdown' and 'no shutdown' commands on the interface to recover from err-disabled state.

Answer

Check the VLAN configuration on SwitchA because the interface is administratively down.

Question 2

A network technician is troubleshooting connectivity between two directly connected Cisco switches. Hosts on VLAN 10 connected to SwitchA cannot ping the default gateway on SwitchB. The interface on SwitchB shows up/up, but the interface on SwitchA shows up/down. The technician examines the interface configuration and status on SwitchA. What is the most likely cause of this issue?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The router is missing a subinterface for VLAN 20.. The PC can ping its default gateway (192.168.10.1) but not the server at 192.168.20.10, indicating Layer 3 routing is failing between VLANs. Since the switch is configured with VLAN 10 for the access port and uses a router-on-a-stick, the router must have a subinterface for VLAN 20 to route traffic to the server's subnet. The absence of a subinterface for VLAN 20 prevents the router from forwarding packets from VLAN 10 to VLAN 20, making option B correct.

Answer

The trunk port Gi1/0/24 is not in trunking mode.

Answer

The switch port Gi1/0/12 is not assigned to VLAN 10.

Answer

The PC has a duplicate IP address with the server.

Question 3

A network administrator notices that the NTP server on Router R1 is not synchronizing with the upstream NTP server at 192.0.2.1. The router is configured as an NTP client, but show ntp status indicates the clock is unsynchronized and the stratum is 16. There is no firewall between R1 and 192.0.2.1. What is the most likely cause of this issue?

Accepted Answer

Router R1 does not have a route to reach 192.0.2.1.. The most likely cause is that Router R1 lacks a route to the upstream NTP server at 192.0.2.1. Without a valid IP route, NTP packets cannot reach the server, so the client remains unsynchronized with stratum 16. The other options are incorrect: A is not required for client operation, C is irrelevant because NTP version negotiation works across versions, and D is ruled out by the absence of a firewall.

Answer

The NTP server at 192.0.2.1 is not configured as a peer on R1.

Answer

The NTP server at 192.0.2.1 is not using NTP version 4.

Answer

The NTP server at 192.0.2.1 has a firewall blocking NTP traffic.

Question 4

R1 and R2 are directly connected. Both are configured in OSPF area 0, and they can successfully ping each other. However, OSPF neighbor adjacency fails. R1's interface is configured with `ip ospf authentication message-digest` and a valid key, while R2's interface has no OSPF authentication configured. What is the most likely cause?

Accepted Answer

The OSPF authentication settings do not match.. The most likely cause is an OSPF authentication mismatch. Although the routers have IP connectivity and are in the same OSPF area, OSPF adjacency requires matching security parameters. R1 uses message-digest authentication whereas R2 has none configured, preventing neighbor formation. The other options are incorrect: the stem confirms they are in the same area (A), OSPF does not require identical hostnames (C), and successful pings prove the subnet mask does not block multicast traffic (D).

Answer

The routers are in different OSPF areas.

Answer

The routers need identical hostnames before adjacency can form.

Answer

The subnet mask prevents OSPF multicast traffic.

Question 5

Which THREE statements accurately describe the role of AI agents in closed-loop remediation workflows for network automation?

Accepted Answer

AI agents can autonomously analyze network telemetry and decide on remediation actions.. B is correct because AI agents in closed-loop remediation workflows autonomously analyze network telemetry (e.g., gRPC, NETCONF) and decide on remediation actions without manual intervention, enabling rapid response. D is correct because tool-calling allows the AI agent to invoke external automation tools like Ansible or Python scripts to execute the chosen remediation steps. E is correct because a key part of the closed-loop is that the AI agent monitors the network after action to confirm the issue is resolved and adjusts if needed, ensuring the loop is closed. A is wrong because closed-loop automation implies autonomous execution based on predefined policies, not requiring manual approval for every action. C is wrong because AI agents use dynamic telemetry and learned patterns, not just static baseline configurations, to detect anomalies. F is wrong because AI agents augment, not eliminate, human oversight; human intervention remains for policy exceptions and oversight.

Answer

AI agents require manual approval before executing any remediation action in a closed-loop workflow.

Answer

AI agents rely solely on static baseline configurations to detect anomalies.

Answer

AI agents eliminate the need for human oversight in network operations.

Question 6

A host at 192.168.50.10/24 needs to send traffic to 192.168.60.20. Which MAC address will it normally place in the Ethernet destination field for the first frame?

Accepted Answer

The MAC address of its configured default gateway. When a host wants to send traffic to a different IP subnet, it does not send the frame directly to the remote device’s MAC address. In plain language, the host knows the destination IP is off its local network, so it hands the traffic to the local router. That means the Ethernet frame is addressed to the default gateway’s MAC address, while the IP packet inside still carries the final remote IP destination.

A host uses ARP to learn MAC addresses on its own LAN. Since the remote host is not local, the sender does not ARP for the remote host’s MAC. Instead, it ARPs for the gateway interface on the same subnet.

Answer

The MAC address of the remote host at 192.168.60.20

Answer

The broadcast MAC address only

Answer

Its own source MAC address

Question 7

Which TWO statements correctly describe the configuration and effect of Root Guard and BPDU Guard on a Cisco switch?

Accepted Answer

Root Guard is configured on a per-port basis and causes the port to become root-inconsistent if a superior BPDU is received.. Root Guard is configured per interface using the 'spanning-tree guard root' command. When a port with Root Guard enabled receives a superior BPDU (one that would cause the switch to become a non-root bridge), the port is placed into a root-inconsistent state, effectively blocking traffic on that port and preventing the switch from accepting a new root bridge from that direction. This protects the spanning-tree topology from unauthorized or misconfigured switches attempting to become the root bridge. Option D is correct because BPDU Guard is commonly enabled on ports with PortFast (typically access ports connected to end devices). When a BPDU is received on such a port, BPDU Guard places the port into errdisable state, preventing potential bridging loops that could result from an unauthorized switch connecting to the network. Option B is incorrect because BPDU Guard does not prevent loops by disabling a trunk port; it is typically used on access ports (often with PortFast) and disables the port upon receiving any BPDU, not just on trunk ports. Option C is incorrect because Root Guard places the port into root-inconsistent state (not errdisable) when a superior BPDU is received; BPDU Guard uses errdisable. Option E is incorrect because neither Root Guard nor BPDU Guard filters BPDUs; Root Guard reacts to superior BPDUs by blocking the port, and BPDU Guard reacts to any BPDU by disabling the port. Both features allow BPDUs to be processed but then take action based on the received BPDUs.

Answer

BPDU Guard prevents loops by disabling a trunk port that receives a BPDU from an unauthorized switch.

Answer

Root Guard places a port in errdisable state when a superior BPDU is received.

Answer

Both Root Guard and BPDU Guard filter BPDUs to prevent them from being processed by the switch CPU.

Question 8

A multilayer switch has working SVIs for VLAN 10 and VLAN 20, but traffic between the VLANs fails. Hosts can ping their own gateway interfaces. Which misconfiguration is most strongly suggested if the SVIs themselves are correct?

Accepted Answer

IP routing is not enabled on the multilayer switch.. IP routing is not enabled. The switch can ping SVIs locally because they are directly connected, but without `ip routing`, it cannot forward packets between VLANs. Option B is wrong because different VLANs require different subnets for routing. Option C is wrong because access ports do not need to be trunks; SVIs handle routing at Layer 3. Option D is wrong because the wireless controller does not provide the default gateway for wired VLAN routing; the SVI does.

Answer

Both VLANs need to use the same IP subnet.

Answer

All access ports must be converted into trunks.

Answer

The wireless controller must provide the default gateway.

Question 9

A packet is destined for 192.168.40.130. The routing table contains 192.168.40.0/24, 192.168.40.128/25, and 0.0.0.0/0. Which route is used?

Accepted Answer

192.168.40.128/25. The /25 route is used because it is the most specific matching prefix. In plain language, even though the /24 and the default route also technically match, the router prefers the entry that most precisely describes the destination range. Since 192.168.40.130 falls inside 192.168.40.128/25, that route wins under longest-prefix match.

This is a classic routing-table interpretation pattern. The router does not start with the default route when more specific routes exist, and it does not choose the /24 simply because it is familiar. Specificity comes first.

Answer

192.168.40.0/24

Answer

0.0.0.0/0

Answer

No route can be used because the entries overlap

Question 10

A router has routes to 192.168.0.0/16 and 192.168.100.0/24. Which route is used for traffic to 192.168.100.77?

Accepted Answer

192.168.100.0/24. The route to 192.168.100.0/24 is used because it is more specific. In plain language, even though the /16 route covers a large address range that includes the destination, the /24 route describes the destination network more precisely. Longest-prefix match therefore prefers the /24.

This is a basic but critical routing-table concept. The router does not choose the broader route when a narrower one matches the same destination.

Answer

192.168.0.0/16

Answer

Both routes are discarded because they overlap.

Answer

The default route is preferred if present.

Question 11

A network operations team is implementing an automated system to detect and remediate interface flapping on core switches. The system must be able to query the network device for interface status and execute commands to disable or reconfigure the interface if a pattern of flapping is detected. Which protocol or technology enables the system to programmatically interact with the network device for both monitoring and configuration changes?

Accepted Answer

NETCONF. NETCONF is the correct choice because it is a standardized network configuration protocol that allows automated systems to retrieve operational data and push configuration changes securely. In this scenario, the system would use NETCONF to query interface status and then apply remediation configurations. SNMP can monitor but has limited configuration capabilities, CLI scripting is non-programmatic and error-prone, and Syslog is only for logging.

Answer

SNMP

Answer

CLI scripting

Answer

Syslog

Question 12

A network technician is troubleshooting connectivity between two directly connected Cisco switches. Hosts on VLAN 10 connected to SwitchA cannot ping the default gateway on SwitchB. The interface on SwitchB shows up/up, but the interface on SwitchA shows up/down. The technician examines the interface configuration and status on SwitchA. What is the most likely cause of this issue?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The problem is at the Application layer (Layer 7); successful operations are at the Application layer (Layer 7) and Transport layer (Layer 4).. The problem is at the Application layer (Layer 7) because the email client can resolve the domain name (DNS, Layer 7), establish a TCP connection (Transport layer, Layer 4), but the mail server returns an application-layer error (e.g., SMTP 550 or 554), indicating the issue lies in the email protocol itself (e.g., authentication failure, mailbox full, or rejected sender). Successful operations include DNS resolution (Application layer) and TCP three-way handshake (Transport layer), confirming layers 7 and 4 are functioning correctly.

Answer

The problem is at the Transport layer (Layer 4); successful operations are at the Application layer (Layer 7) only.

Answer

The problem is at the Network layer (Layer 3); successful operations are at the Data Link layer (Layer 2) and Physical layer (Layer 1).

Answer

The problem is at the Presentation layer (Layer 6); successful operations are at the Session layer (Layer 5) and Transport layer (Layer 4).

Question 13

Which TWO statements correctly describe the configuration and use of a voice VLAN on a Cisco switch port?

Accepted Answer

When a voice VLAN is configured, the switch port operates in two VLANs: one for data and one for voice traffic.. When a voice VLAN is configured on a Cisco switch port, the port operates in two separate VLANs simultaneously: one for data traffic (the access VLAN) and one for voice traffic (the voice VLAN). This is achieved using the 'switchport voice vlan' command, which allows the switch to tag voice frames with the voice VLAN ID while leaving data frames untagged (or tagged with the access VLAN). This separation ensures that voice traffic receives appropriate QoS treatment and is isolated from data traffic.

Answer

The voice VLAN is configured using the 'switchport mode trunk' command.

Answer

The voice VLAN must be the same as the native VLAN on the trunk link.

Answer

The data VLAN and voice VLAN must be in the same IP subnet.

Question 14

Match each common automation term to its most accurate meaning.

Accepted Answer

Infrastructure as Code: Managing infrastructure through machine-readable definition files. Infrastructure as Code (IaC) refers to managing and provisioning infrastructure through machine-readable definition files, enabling automation and version control. Idempotence means that performing the same operation multiple times results in the same state, ensuring consistency. The declarative model allows the user to define the desired end state, and the system automatically determines how to achieve it. In contrast, the imperative model requires the user to specify step-by-step instructions to reach the desired state. These four terms are fundamental to understanding network automation approaches.

Question 15

Match each automation-related term to the description that best fits it.

Accepted Answer

Idempotent: An operation that can be applied multiple times without changing the result beyond the initial application.. The question requires matching automation-related terms to their correct descriptions. Idempotent means that an operation can be applied multiple times without changing the result after the first application. Declarative is a style where the user defines the desired state and the system determines the steps to achieve it. Imperative is a style where explicit step-by-step instructions are given. Orchestration refers to the automated coordination of multiple systems or services to complete a workflow. Each description aligns precisely with these concepts.