N10-009 Practice Test 3 — 30 Questions

Question 1

A network administrator scheduled a change window to upgrade the firmware on a core switch. During the upgrade, the switch fails to boot properly. The administrator needs to restore the switch to its previous operational state. Which of the following should the administrator have done before the upgrade to facilitate a successful rollback?

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

Accepted Answer

Backed up the current configuration and firmware image.. Backing up both the current configuration and the firmware image ensures that the administrator can restore the switch to its exact previous operational state if the upgrade fails. Without a backup of the firmware image, the switch may not have a valid bootable image to revert to, even if the configuration is saved. This is a fundamental prerequisite for any firmware upgrade rollback plan.

Answer

Notified all users of the maintenance window.

Answer

Disconnected all redundant links.

Answer

Set the switch to boot from an alternative image.

Question 2

A network technician is troubleshooting an issue where Server A can ping Server B by IP address, but Server B cannot ping Server A. Both servers are in the same VLAN and subnet, connected to the same switch. The switch ports are configured identically, and there are no ACLs or firewalls between them. Which of the following is the MOST likely cause?

Accepted Answer

Server A's firewall is blocking incoming ICMP. Server A can ping Server B by IP address, meaning ICMP echo requests from Server A reach Server B and echo replies return successfully. However, Server B cannot ping Server A, which indicates that ICMP echo requests from Server B are not reaching Server A or their replies are blocked. Since both servers are in the same VLAN/subnet with no ACLs or firewalls between them, the most likely cause is that Server A's host-based firewall is blocking incoming ICMP (echo requests), preventing Server B's pings from being processed. This is a classic symptom of a one-way firewall rule that permits outbound ICMP but denies inbound ICMP.

Answer

Server B's firewall is blocking outgoing ICMP

Answer

The cable connecting Server A is faulty

Answer

There is a duplex mismatch on Server B's switch port

Question 3

A network engineer is configuring a Link Aggregation Group (LAG) between two switches. Switch A is set to LACP active mode. Which mode should be configured on Switch B to form the LAG?

Accepted Answer

Passive. LACP active mode initiates negotiation by sending LACP packets, while passive mode responds to those packets without initiating. Since Switch A is set to active, Switch B must be in passive mode to successfully form a Link Aggregation Group (LAG). This combination allows the two switches to exchange LACP frames and agree on the aggregation parameters.

Answer

On

Answer

Static

Answer

Auto

Question 4

A network administrator is configuring a syslog server to receive logs from network devices. The administrator wants to capture all messages with a severity level of 'critical' (2) and higher (more severe). What severity threshold should be set on the devices?

Accepted Answer

2 (critical). Syslog severity levels are numbered 0 (most severe) through 7 (least severe). When you set a severity threshold on a device, it captures messages at that level and all lower-numbered (more severe) levels. To capture 'critical' (2) and higher (i.e., levels 0, 1, and 2), you must set the threshold to 2. Option C is correct because level 2 includes itself and all more severe levels (0 and 1).

Answer

0 (emergency)

Answer

1 (alert)

Answer

3 (error)

Question 5

A user reports that they cannot access any network resources. The technician runs 'ipconfig' on the workstation and sees that the IP address is 169.254.23.45 with a subnet mask of 255.255.0.0. What is the most likely cause of this issue?

Accepted Answer

The DHCP server is unreachable or not functioning.. The IP address 169.254.23.45 with a subnet mask of 255.255.0.0 is an Automatic Private IP Addressing (APIPA) address, which is assigned by the operating system when a DHCP discovery attempt fails. This indicates that the workstation was unable to contact a DHCP server to obtain a valid IP configuration, making an unreachable or non-functioning DHCP server the most likely cause.

Answer

The workstation's network cable is unplugged.

Answer

The DNS server is not responding.

Answer

The workstation has been assigned a static IP address in the wrong subnet.

Question 6

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.

Answer

B) Perform an SNMP walk of the interface OIDs

Answer

C) Use SNMP get to retrieve interface status periodically

Answer

D) Configure SNMP set to change interface parameters

Question 7

A security engineer is configuring port security on a switch to prevent unauthorized devices from connecting. The requirement is that only the first device to connect to a port is allowed, and if a different device connects, the port should be disabled. Which port security violation mode should be configured?

Accepted Answer

Shutdown. The 'shutdown' violation mode disables the port entirely when a violation occurs, which meets the requirement that the port be disabled if a different device connects. This is the only mode that physically err-disables the port, preventing any further traffic until manually re-enabled.

Answer

Protect

Answer

Restrict

Answer

Sticky

Question 8

A security auditor discovers that an unauthorized switch has been connected to an access port in the wiring closet. The rogue switch caused a network loop and disrupted connectivity. Which security feature, if enabled on the access port, would have prevented this by disabling the port when a BPDU is received?

Accepted Answer

BPDU guard. BPDU guard is the correct answer because it is specifically designed to protect against rogue switch connections on access ports. When enabled, if a port receives any Bridge Protocol Data Unit (BPDU), it immediately places the port into an errdisable state, effectively disabling it and preventing a potential network loop. This directly addresses the scenario where an unauthorized switch connected to an access port caused a loop.

Answer

Root guard

Answer

Loop guard

Answer

UDLD

Question 9

A network engineer needs to create subnets for four departments, each requiring at least 50 host addresses. The available network is 192.168.1.0/24. Which subnet mask should be used to satisfy the requirements while minimizing wasted addresses?

Accepted Answer

/26 (255.255.255.192). A /26 subnet mask (255.255.255.192) provides 62 usable host addresses per subnet (2^(32-26) - 2 = 62), which meets the requirement of at least 50 hosts per department. With a /24 network, you can create exactly four /26 subnets (192.168.1.0/26, 192.168.1.64/26, 192.168.1.128/26, 192.168.1.192/26), perfectly matching the four departments while minimizing wasted addresses.

Answer

/25 (255.255.255.128)

Answer

/27 (255.255.255.224)

Answer

/24 (255.255.255.0)

Question 10

A workstation with IP address 10.0.1.5/24 needs to communicate with a server at 10.0.2.10/24. The workstation's default gateway is configured as 10.0.1.1. Which of the following will the workstation do with the IP packets destined for the server?

Accepted Answer

Send the packets to the default gateway.. The workstation's IP address (10.0.1.5/24) and the server's IP address (10.0.2.10/24) are on different subnets (10.0.1.0/24 vs. 10.0.2.0/24). When a host determines that the destination is not on the same local network, it will not attempt direct delivery via ARP. Instead, it forwards the IP packet to its configured default gateway (10.0.1.1), which then routes the packet toward the server's subnet.

Answer

Send the packets directly to the server using ARP.

Answer

Send the packets to the DNS server for resolution.

Answer

Drop the packets because the server is on a different network.

Question 11

Users in a warehouse report that their wireless tablets lose connectivity when moving near large metal racks. The signal strength remains high but throughput drops significantly. What is the most likely cause?

Accepted Answer

Multipath interference. When wireless signals reflect off large metal surfaces, multiple copies of the signal arrive at the receiver at slightly different times, causing multipath interference. This phase cancellation effect corrupts the signal, forcing the 802.11 MAC layer to retransmit frames, which drastically reduces throughput even though the received signal strength indicator (RSSI) remains high. The metal racks in the warehouse act as reflective surfaces, creating a classic multipath environment.

Answer

Signal attenuation

Answer

Co-channel interference

Answer

Insufficient DHCP scope

Question 12

An organization wants to centrally manage and monitor network devices from a single interface. The solution should support auto-discovery, configuration management, and performance monitoring. Which type of system should be deployed?

Accepted Answer

Network Management System (NMS). A Network Management System (NMS) is the correct choice because it provides a centralized interface for auto-discovery (e.g., via SNMP or CDP/LLDP), configuration management (e.g., using NETCONF or CLI scripting), and performance monitoring (e.g., polling SNMP MIBs or streaming telemetry). This directly matches the requirement for a single-pane-of-glass solution for network device lifecycle management.

Answer

AAA server

Answer

SIEM

Answer

DHCP server

Question 13

Which of the following security mechanisms requires a user to authenticate before gaining access to the wired network at a switch port?

Accepted Answer

802.1X. 802.1X is a port-based Network Access Control (NAC) standard (IEEE 802.1X) that requires a user or device to authenticate via an authentication server (e.g., RADIUS) before the switch port transitions from an unauthorized to an authorized state, allowing full network access. It uses Extensible Authentication Protocol (EAP) over LAN (EAPoL) to carry authentication messages between the supplicant (client), authenticator (switch), and authentication server. This ensures that only authenticated users can access the wired network at the switch port level.

Answer

Port security

Answer

ACL

Answer

MAC authentication

Question 14

A router receives a packet destined for 10.0.0.15. It has the following routes in the routing table: 10.0.0.0/8 via 192.168.1.1, 10.0.0.0/16 via 192.168.2.1, 0.0.0.0/0 via 192.168.3.1. Which route will be used?

Accepted Answer

10.0.0.0/16 via 192.168.2.1. The router will use the route 10.0.0.0/16 via 192.168.2.1 because it has the longest prefix match (16 bits) for the destination 10.0.0.15. The /16 route is more specific than the /8 route and the default route, so it is preferred regardless of administrative distance or metric.

Answer

Default route (0.0.0.0/0)

Answer

10.0.0.0/8 via 192.168.1.1

Answer

None; the packet is dropped

Question 15

A network engineer needs to connect two devices that are 150 meters apart with a 10 Gbps link. Which cabling type is most suitable?

Accepted Answer

Single-mode fiber. Single-mode fiber (SMF) is the correct choice because it supports 10 Gbps transmission over distances well beyond 150 meters, typically up to 10 km or more using 10GBASE-LR optics. In contrast, copper cabling like Cat6a or Cat7 is limited to 100 meters for 10GBASE-T, and multimode fiber (MMF) with 10GBASE-SR is limited to about 300-400 meters depending on the fiber grade (e.g., OM3/OM4), but SMF provides the most reliable and future-proof solution for this distance.

Answer

Cat6a UTP

Answer

Cat7 STP

Answer

Multimode fiber

Question 16

A network technician configures an 802.1Q trunk link between two switches. After the configuration, VLAN 20 traffic is not passing across the trunk, although VLAN 10 traffic works fine. The technician verifies that both switches have VLAN 20 created and that the trunk is up. What is the most likely cause?

Accepted Answer

VLAN 20 is not included in the allowed VLAN list on the trunk.. The most likely cause is that VLAN 20 is not included in the allowed VLAN list on the trunk. By default, an 802.1Q trunk allows all VLANs, but if the allowed VLAN list has been manually configured or pruned, VLAN 20 may have been excluded. Since VLAN 10 works, the trunk is operational, and both switches have VLAN 20 created, the issue is specifically that the trunk is not permitting VLAN 20 traffic.

Answer

The native VLAN is mismatched between the switches.

Answer

The trunk port is set to dynamic desirable mode.

Answer

The encapsulation type is ISL instead of 802.1Q.

Question 17

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.

Answer

The router subinterface for VLAN 20 is not enabled.

Answer

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

Answer

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

Question 18

A network engineer is troubleshooting a communication issue between two hosts. The engineer determines that the data is being segmented at the source and reassembled at the destination, but the segments are arriving out of order. Which OSI layer is responsible for sequencing the segments?

Accepted Answer

D) Transport layer. The Transport layer (Layer 4) is responsible for end-to-end communication, including segmentation, reassembly, and sequencing of data segments. Protocols like TCP use sequence numbers to order segments correctly at the destination, even if they arrive out of order. This ensures the upper layers receive a complete, ordered data stream.

Answer

A) Physical layer

Answer

B) Data Link layer

Answer

C) Network layer

Question 19

A network administrator is troubleshooting communication between two switches connected via a trunk port. The trunk link is up/up, but devices in VLAN 20 cannot communicate across the trunk. The administrator has verified that both switches have VLAN 20 created and that the access ports are configured correctly. Which command should the administrator run on each switch to verify the trunk's allowed VLAN list?

Accepted Answer

show interfaces trunk. The 'show interfaces trunk' command displays the trunking status, including the allowed VLAN list on the trunk port. Since the trunk link is up/up but VLAN 20 traffic fails, the most likely cause is that VLAN 20 is not included in the allowed VLAN list on one or both switches. This command directly shows which VLANs are permitted, pruned, or active on the trunk.

Answer

show vlan brief

Answer

show running-config interface

Answer

show mac address-table

Question 20

A security administrator is configuring a wireless network to use WPA3-Enterprise. Which authentication server protocol is required for WPA3-Enterprise?

Accepted Answer

RADIUS. WPA3-Enterprise requires 802.1X/EAP authentication, which uses RADIUS as the backend authentication server protocol. RADIUS handles the exchange of EAP frames between the authenticator (access point) and the authentication server, enforcing per-user credentials and supporting the mandatory 192-bit security suite for WPA3-Enterprise. Without RADIUS, the 802.1X framework cannot operate, making it the only required protocol for this deployment.

Answer

LDAP

Answer

TACACS+

Answer

Kerberos