N10-009 Practice Test 37 — 15 Questions

Question 1

At which OSI layer does a router primarily operate to make forwarding decisions based on IP addresses?

Accepted Answer

Layer 3 (Network). A router primarily operates at Layer 3 (Network) of the OSI model because it uses logical IP addresses (e.g., IPv4 or IPv6) to make forwarding decisions. The router examines the destination IP address in the packet header, performs a longest-prefix match against its routing table, and determines the next-hop interface. This layer is responsible for end-to-end delivery and path selection across multiple networks.

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Layer 1 (Physical)

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Layer 2 (Data Link)

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Layer 4 (Transport)

Question 2

Which device operates at Layer 1 (Physical) of the OSI model and regenerates electrical signals to extend the distance of a network segment?

Accepted Answer

Hub. A hub operates at Layer 1 (Physical) of the OSI model. It receives incoming electrical signals on one port and regenerates (repeats) those signals out to all other ports, effectively extending the physical reach of a network segment. Unlike switches or routers, it performs no frame inspection or forwarding decisions.

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Switch

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Router

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Bridge

Question 3

A network administrator wants to be alerted immediately when any interface on a core router goes down. The administrator has already configured SNMP community strings. Which additional configuration is necessary to receive these alerts?

Accepted Answer

A) Configure the router to send SNMP traps to the NMS. SNMP traps are unsolicited notifications sent from the managed device (the router) to the Network Management Station (NMS) when a specific event occurs, such as an interface going down. Since the administrator wants immediate alerts without polling, configuring the router to send SNMP traps to the NMS is the correct approach. The SNMP community strings are already set, so the missing piece is the trap destination and enabling trap generation for interface state changes.

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B) Perform an SNMP walk of the interface OIDs

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C) Use SNMP get to retrieve interface status periodically

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D) Configure SNMP set to change interface parameters

Question 4

A network administrator configures VLAN 10 (Sales) and VLAN 20 (Engineering) on a switch. The switch is connected to a router via a trunk interface for inter-VLAN routing. Users in VLAN 10 can reach the router and external networks, but users in VLAN 20 cannot communicate outside their VLAN. The router's subinterface for VLAN 20 is configured correctly with an IP address and encapsulation dot1Q 20. What is the MOST likely cause of the issue?

Accepted Answer

B: VLAN 20 is not allowed on the trunk. The router's subinterface for VLAN 20 is correctly configured, so the issue lies on the switch side. If VLAN 20 is not explicitly allowed on the trunk interface connecting the switch to the router, frames from VLAN 20 will be dropped by the switch, preventing inter-VLAN routing. The default trunk allowed VLAN list often includes only VLAN 1, so VLAN 20 must be added with the 'switchport trunk allowed vlan add 20' command.

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A: The switchport mode for VLAN 20 is set to access

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C: The router needs to be rebooted to apply the subinterface configuration

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D: The native VLAN on the trunk is misconfigured

Question 5

Users in a remote office are experiencing slow file transfers to the data center. The network technician runs a traceroute and discovers high latency on a specific hop. The technician pings that hop and gets replies with varying latency. The technician also checks the interface error counters on the router at that hop and finds no errors. What is the most likely cause?

Accepted Answer

CPU overload on the router. High latency with varying values (jitter) combined with clean interface error counters points to a router that is overwhelmed by processing demands. When a router's CPU is overloaded, it queues packets for processing, introducing variable delays even though the physical layer shows no errors. This matches the symptom of a specific hop showing latency spikes without CRC or framing errors.

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Duplex mismatch

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Incorrect MTU

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Route flapping

Question 6

A company wants to prevent unauthorized devices from connecting to the wired network by authenticating users or devices before granting network access. Which of the following technologies should be implemented on the switch ports to achieve this?

Accepted Answer

A: 802.1X. 802.1X is an IEEE standard (802.1X-2020) for port-based Network Access Control (NAC). It authenticates users or devices via EAP (Extensible Authentication Protocol) before the switch port transitions from the unauthorized (blocking) state to the authorized (forwarding) state, effectively preventing unauthorized devices from accessing the wired network.

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B: Port security with MAC address sticky

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C: Access control lists (ACLs)

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D: DHCP snooping

Question 7

A network administrator configures a trunk link between two switches. The link is up, but no traffic from any VLAN is passed between the switches. The administrator verifies that the trunk port is configured correctly on both switches with 'switchport mode trunk' and allowed VLANs. Which of the following is the most likely cause?

Accepted Answer

The trunk encapsulation is mismatched. Option D is correct because a trunk link requires both ends to use the same encapsulation protocol—either 802.1Q or ISL. If one switch is set to 'switchport trunk encapsulation dot1q' and the other uses 'isl' (or auto-negotiates to a different type), the frames will be dropped or misinterpreted, preventing any VLAN traffic from passing. The administrator verified 'switchport mode trunk' and allowed VLANs, but encapsulation mismatch is a common oversight that stops all VLAN traffic while keeping the link up.

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The native VLAN is different on each switch

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VLAN 1 has been deleted on one of the switches

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Spanning Tree Protocol is blocking the trunk link

Question 8

A network administrator adds a new server to VLAN 20. The switch port is configured as an access port in VLAN 20, and the server has a correct static IP address in that subnet. However, the server cannot communicate with other devices in the same VLAN. The VLAN exists on the switch and other devices in VLAN 20 are working. What is the most likely cause of this issue?

Accepted Answer

The switch port is configured as a trunk port instead of an access port. The scenario states the switch port is configured as an access port in VLAN 20, but the server cannot communicate with other devices in the same VLAN. If the port were actually configured as a trunk port, it would expect frames to be tagged with a VLAN ID. An untagged frame from the server would be placed into the native VLAN (typically VLAN 1), not VLAN 20, causing a mismatch. This explains why the server, despite having a correct static IP in VLAN 20's subnet, cannot reach other devices in VLAN 20.

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VLAN 20 is not allowed on the trunk to the router

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The server does not have a default gateway configured

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The port is administratively down

Question 9

A network administrator is configuring a router-on-a-stick to route between two VLANs (VLAN 10 and VLAN 20). The router has two subinterfaces: GigabitEthernet0/1.10 with encapsulation dot1Q 10 and IP 10.10.10.1/24, and GigabitEthernet0/1.20 with encapsulation dot1Q 20 and IP 10.10.20.1/24. The switch port connected to the router is configured as an access port in VLAN 10. Hosts in VLAN 10 can ping the router's VLAN 10 interface, but hosts in VLAN 20 cannot ping the router's VLAN 20 interface. What is the most likely cause?

Accepted Answer

The switch port connecting to the router should be configured as a trunk.. The router-on-a-stick design requires the switch port connecting to the router to be configured as a trunk port, not an access port. An access port only carries traffic for a single VLAN (VLAN 10 in this case), so frames from VLAN 20 are dropped at the switch port before reaching the router. Configuring the port as a trunk with allowed VLANs 10 and 20 would enable the router's subinterfaces to receive and forward traffic for both VLANs.

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The router subinterface for VLAN 20 is not enabled.

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The hosts in VLAN 20 do not have a default gateway configured.

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The router's VLAN 20 subinterface has an incorrect IP address.

Question 10

What is the default administrative distance for OSPF routes on a typical Cisco router?

Accepted Answer

110. Option C is correct because the default administrative distance for OSPF routes on a Cisco router is 110. Administrative distance is a trustworthiness metric used to select the best route when multiple routing protocols provide a route to the same destination; a lower value is preferred. OSPF's default AD of 110 is higher than that of static routes (1) and EIGRP (90/170), but lower than RIP (120) and IS-IS (115).

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90

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100

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120

Question 11

A network administrator needs to connect two switches located in separate buildings 150 meters apart. The connection must support 10 Gbps speeds. Which cabling type is most appropriate?

Accepted Answer

Multi-mode fiber optic. Multi-mode fiber optic (MMF) is the most appropriate choice because it supports 10 Gbps speeds over distances up to 300 meters (using OM3 or OM4 fiber) with cost-effective transceivers (e.g., 10GBASE-SR). The 150-meter distance exceeds the 100-meter maximum for twisted-pair copper cabling (Cat6a or Cat7) at 10 Gbps, making fiber the only viable option among the choices.

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Cat6a twisted pair

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Cat7 twisted pair

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Single-mode fiber optic

Question 12

A network administrator needs to ensure that in the event of a switch failure, the switch can be replaced and brought online with minimal downtime. Which of the following tasks should the administrator perform regularly?

Accepted Answer

Back up the configuration files of all switches. Regularly backing up the configuration files of all switches ensures that when a failed switch is replaced, the exact configuration can be restored quickly, minimizing downtime. This is a core best practice in network operations because a replacement switch typically ships with factory defaults and requires the original configuration to resume normal operations. Without a recent backup, the administrator would have to reconfigure the switch manually, leading to extended outage and potential human error.

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Perform a firmware upgrade on all switches

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Monitor the switch's CPU utilization

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Create a network performance baseline

Question 13

A network administrator notices that a large number of ICMP echo request packets are being sent to the broadcast address of the network from a single host. This is causing performance degradation. Which type of attack is this?

Accepted Answer

Smurf attack. The smurf attack exploits ICMP by sending echo request packets to a network's broadcast address with a spoofed source IP of the victim. All hosts on the network then reply to the victim, overwhelming it with traffic and causing performance degradation. This matches the scenario of a single host sending ICMP echo requests to the broadcast address.

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ARP spoofing

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MAC flooding

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DNS amplification

Question 14

A network administrator wants to automate IP address assignment for client devices. Which protocol should be used?

Accepted Answer

DHCP. DHCP (Dynamic Host Configuration Protocol) automates IP address assignment by leasing IP configurations to client devices from a defined pool. This eliminates the need for manual static IP configuration, making it the correct protocol for automated IP address management.

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DNS

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ARP

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ICMP

Question 15

A network administrator needs to ensure high availability for a critical server that has two network interfaces connected to two different switches. Which configuration should be implemented to provide failover and load balancing at the network layer?

Accepted Answer

Virtual IP (VRRP/HSRP). Virtual IP protocols like VRRP or HSRP provide first-hop redundancy by allowing two or more routers (or servers acting as routers) to share a virtual IP address. If the active interface fails, the standby interface takes over the virtual IP, ensuring seamless failover at Layer 3. Additionally, with multiple virtual IP groups, traffic can be load-balanced across the two interfaces, meeting both high-availability and load-balancing requirements at the network layer.

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Link aggregation (LACP)

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Spanning Tree Protocol (STP)

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Port mirroring