N10-009 Practice Exam 2 — 20 Questions

Question 1

Which layer of the OSI model is responsible for logical addressing and routing of packets between networks?

Accepted Answer

Network layer. The Network layer (Layer 3) is responsible for logical addressing (e.g., IPv4/IPv6 addresses) and routing packets between different networks by determining the best path using routing protocols such as OSPF, BGP, or static routes. Unlike the Data Link layer, which handles physical addressing (MAC) within a single network segment, the Network layer enables end-to-end delivery across multiple hops.

Answer

Data Link layer

Answer

Transport layer

Answer

Application layer

Question 2

A network administrator reviews firewall logs and sees thousands of SYN packets coming from various source IP addresses to a single internal web server. No ACK or RST packets are observed from these sources. Which type of attack is most likely occurring?

Accepted Answer

SYN flood attack. A SYN flood attack exploits the TCP three-way handshake by sending a high volume of SYN packets to a target server without completing the handshake (no ACK or RST). This exhausts the server's connection table resources, preventing legitimate connections. The observed pattern of many SYN packets from various sources with no subsequent ACK or RST is the hallmark of a SYN flood.

Answer

DNS amplification attack

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ARP spoofing attack

Answer

Man-in-the-middle attack

Question 3

A new switch is installed in a remote wiring closet. It has been configured with a management IP address of 10.1.2.50/24. The switch is connected via a trunk to the distribution switch, and the management station (10.1.1.0/24) is on a different subnet. The switch cannot be pinged from the management station. The distribution switch has routing to the 10.1.2.0/24 subnet. What is the most likely cause?

Accepted Answer

The default gateway is not configured on the new switch.. The management station is on subnet 10.1.1.0/24, while the switch's management IP is 10.1.2.50/24. For the switch to reply to pings from a different subnet, it must have a default gateway configured so it knows where to send return traffic. Without a default gateway, the switch will only respond to traffic on its local subnet, making it unreachable from the management station.

Answer

The management VLAN is not allowed on the trunk.

Answer

The switch port to the distribution switch is in access mode.

Answer

The management IP is configured on the wrong VLAN.

Question 4

A user reports that they cannot access the internet. The technician tests connectivity: pinging the default gateway succeeds, but pinging a public IP address like 8.8.8.8 fails. Firewall logs show outbound ICMP to 8.8.8.8 is permitted. What is the most likely cause?

Accepted Answer

Missing default route on the router. The user can ping the default gateway (local connectivity) but cannot ping a public IP like 8.8.8.8. This indicates that the workstation has a valid route to its local subnet, but the router lacks a default route (0.0.0.0/0) to forward traffic to the internet. Firewall logs confirm outbound ICMP is permitted, so the issue is at Layer 3 routing, not filtering.

Answer

Incorrect DNS configuration on the workstation

Answer

Duplicate IP address on the local network

Answer

Proxy server configuration is required

Question 5

A network administrator wants to ensure all network devices have synchronized time for accurate log correlation and security event analysis. Which protocol should be implemented?

Accepted Answer

NTP. NTP (Network Time Protocol) is the correct choice because it is specifically designed to synchronize clocks across network devices using a hierarchical system of time sources, ensuring millisecond-level accuracy. Accurate time synchronization is critical for correlating logs and security events across multiple devices, as timestamps must match to reconstruct attack timelines or diagnose faults.

Answer

SNMP

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FTP

Answer

HTTP

Question 6

A user reports that they cannot connect to a file server on the same subnet. The technician checks the workstation's IP configuration: IP 192.168.1.10, subnet mask 255.255.255.0, default gateway 192.168.1.1. The workstation can ping the gateway but cannot ping the file server at 192.168.1.50. Which of the following is the most likely cause?

Accepted Answer

The file server is powered off or disconnected from the network. The workstation can ping the gateway (192.168.1.1) but not the file server (192.168.1.50) on the same subnet. Since both are on the same subnet, the default gateway is not needed for local traffic. The inability to ping the server suggests the server itself is not responding. The most likely causes are that the server is powered off, its network cable is disconnected, or it has a failed network interface. A firewall blocking ICMP would also prevent ping, but the question specifies that the correct answer is the server being powered off or disconnected (option C). Therefore, the most likely cause is that the file server is powered off or has a disconnected cable.

Answer

Incorrect subnet mask on the workstation

Answer

Incorrect default gateway on the workstation

Answer

A firewall on the workstation is blocking traffic to the server

Question 7

A network administrator is configuring a new switch to carry traffic for multiple VLANs on a single link to a router. Which IEEE standard is used for VLAN tagging on Ethernet trunks?

Accepted Answer

802.1Q. 802.1Q is the IEEE standard that defines VLAN tagging on Ethernet trunks, inserting a 4-byte tag into the Ethernet frame to identify VLAN membership. This allows multiple VLANs to traverse a single link between a switch and a router, enabling inter-VLAN routing without separate physical interfaces.

Answer

802.3af

Answer

802.1D

Answer

802.11ac

Question 8

A switch port is configured as a trunk with native VLAN 99. When a frame tagged with VLAN 99 is received on the trunk, the switch displays an error. What is the most likely issue?

Accepted Answer

The remote switch is tagging frames on the native VLAN. The native VLAN is the VLAN that carries untagged traffic on an 802.1Q trunk. By design, frames belonging to the native VLAN should be sent untagged. When a switch receives a frame tagged with the native VLAN ID (VLAN 99), it indicates a mismatch in native VLAN configuration between the two ends of the trunk. The switch logs an error because it expects native VLAN frames to be untagged, but the remote switch is incorrectly tagging them.

Answer

The trunk is using 802.1Q encapsulation and the remote switch expects ISL

Answer

The remote switch is sending frames on VLAN 99 as untagged

Answer

The allowed VLAN list does not include VLAN 99

Question 9

A network administrator has just connected a new access switch to the core switch via a trunk port. The administrator configured the trunk port on both switches with the same allowed VLAN list. However, hosts on VLAN 10 connected to the new access switch cannot communicate with hosts on VLAN 10 on the core switch. The trunk is operational and shows up/up. What is the most likely cause?

Accepted Answer

A) VLAN 10 has not been created on the new access switch. The most likely cause is that VLAN 10 has not been created on the new access switch. Even though the trunk port is up/up and the allowed VLAN list matches, a switch will not forward traffic for a VLAN that does not exist in its local VLAN database. Without the VLAN being created, the switch drops all frames tagged with VLAN 10, preventing communication between hosts on that VLAN across the trunk.

Answer

B) Native VLAN mismatch on the trunk

Answer

C) Trunk encapsulation mismatch (ISL vs 802.1Q)

Answer

D) STP is blocking the VLAN 10 traffic on the trunk

Question 10

A network administrator is preparing to upgrade the firmware on a critical router. Which document should the administrator consult to understand the steps required to minimize downtime and ensure a successful upgrade?

Accepted Answer

Change management plan. The change management plan documents the approved procedures, rollback steps, and communication protocols for performing maintenance on critical infrastructure. Consulting this plan ensures the administrator follows the organization's predefined steps to minimize downtime and mitigate risks during the firmware upgrade.

Answer

SLA

Answer

Network diagram

Answer

Baseline performance report

Question 11

After replacing a faulty network cable, a user reports that they can access local resources but not the internet. The technician verifies that the user's IP address is 192.168.1.100 with a subnet mask of 255.255.255.0 and a default gateway of 192.168.1.1. The technician can ping the default gateway successfully. Which of the following should the technician check NEXT?

Accepted Answer

A) DNS configuration. The user can access local resources and successfully ping the default gateway, which confirms that Layer 2 and Layer 3 connectivity to the local network is working. The inability to access the internet while local access works points to a name resolution failure, as the browser relies on DNS to translate domain names to IP addresses. Checking DNS configuration is the logical next step because a misconfigured or missing DNS server would prevent internet access even when IP connectivity is intact.

Answer

B) DHCP server

Answer

C) Router's firewall ACLs

Answer

D) Switch port VLAN assignment

Question 12

Users in VLAN 10 cannot obtain IP addresses from the DHCP server located in VLAN 20. The router interface for VLAN 10 has an ip helper-address 192.168.20.5 command configured, and users can ping the DHCP server IP (192.168.20.5) from the router. However, users receive APIPA addresses. What is the most likely cause?

Accepted Answer

The DHCP server does not have a scope configured for the 192.168.1.0/24 subnet (VLAN 10). The ip helper-address command on the router correctly forwards DHCPDISCOVER broadcasts from VLAN 10 to the DHCP server at 192.168.20.5. Since users can ping the server from the router, Layer 3 connectivity exists. However, the DHCP server must have a scope (or address pool) for the subnet of the requesting clients (192.168.1.0/24) to offer an IP address; without it, the server ignores the request, and clients fall back to APIPA (169.254.x.x).

Answer

The router's ip helper-address is configured on the wrong interface

Answer

The switch port connecting users is configured as a trunk instead of an access port

Answer

The router's ACL is blocking DHCP offers from the server

Question 13

A user reports that they cannot access the internet, but they can access local resources on the same subnet. The network administrator pings the default gateway and gets a response. Which tool should be used next to trace the path to an external website?

Accepted Answer

traceroute. B is correct because traceroute (tracert on Windows) is the appropriate tool to identify where packets are being dropped or delayed along the path from the local host to an external website. Since the user can access local resources and the default gateway responds to pings, the issue likely lies beyond the gateway, and traceroute will reveal the hop where connectivity fails.

Answer

netstat

Answer

nslookup

Answer

arp

Question 14

A security analyst observes that an internal server is sending a large volume of TCP SYN packets to various external IP addresses, but never completing the three-way handshake. This behavior is indicative of which type of attack?

Accepted Answer

SYN flood attack. A SYN flood attack occurs when an attacker sends a high volume of TCP SYN packets to a target but never completes the three-way handshake by sending the final ACK. This leaves the target's connection table half-open, consuming resources and potentially exhausting its ability to accept legitimate connections. The observed behavior—internal server sending many SYN packets without completing the handshake—matches the classic signature of a SYN flood, though typically the attacker spoofs the source IP to avoid response traffic.

Answer

Man-in-the-middle attack

Answer

DDoS amplification attack

Answer

Smurf attack

Question 15

A user reports that they can access the company's internal web server by IP address (10.10.10.100) but cannot access it by its hostname (intranet.company.com). The user's workstation is configured with the correct internal DNS server address. Which of the following should the technician do FIRST?

Accepted Answer

Check the DNS server's A record for intranet.company.com. The user can reach the server by IP but not by hostname, which indicates a DNS resolution problem. Since the workstation is configured with the correct internal DNS server, the most likely cause is a missing or incorrect A record for intranet.company.com on that DNS server. Checking the A record is the logical first step before other troubleshooting.

Answer

Review the firewall rules on the server

Answer

Run ipconfig /flushdns on the workstation

Answer

Verify the default gateway configuration

Question 16

A network technician notices that a switch port connected to a user's computer is showing a high number of CRC errors and late collisions. The link is operating at 100 Mbps, full duplex according to the switch. Which of the following is the most likely cause of these errors?

Accepted Answer

Duplex mismatch. CRC errors and late collisions in a full-duplex link are classic symptoms of a duplex mismatch. When one side is set to full duplex and the other to half duplex, the half-duplex side does not sense the carrier before transmitting, leading to collisions that are detected late in the frame. The switch reports full duplex, so the user's NIC is likely stuck at half duplex, causing these errors.

Answer

Cable length exceeds 100 meters

Answer

Faulty switch port

Answer

Electromagnetic interference

Question 17

A user reports that they can access the internet but cannot access the company's internal web application at https://intranet.company.local. The technician can ping the server's IP address (192.168.10.50) successfully from the user's workstation. However, when the technician runs 'nslookup intranet.company.local', it returns 'Non-existent domain'. What is the most likely cause?

Accepted Answer

The client's DNS server does not have a record for the internal domain.. The user can access the internet and ping the server's IP address, which confirms Layer 3 connectivity and that the web server is reachable. However, 'nslookup intranet.company.local' returns 'Non-existent domain', indicating that the DNS server used by the client does not have an A or CNAME record for that internal hostname. Since the browser relies on DNS resolution to translate the FQDN to an IP address, the failure to resolve the name prevents the web application from loading, even though the server itself is online and reachable.

Answer

The web server is not running on port 443.

Answer

A firewall is blocking traffic to the internal web server.

Answer

The hostname is misspelled in the browser.

Question 18

A network administrator connects two switches with a trunk link that is configured to allow all VLANs. Workstations in VLAN 10 can communicate across the switches, but workstations in VLAN 20 cannot. Both VLANs are configured on the first switch. What is the most likely cause of the issue?

Accepted Answer

VLAN 20 is not created on the second switch.. VLAN 20 is configured on the first switch but not on the second switch. Even though the trunk link allows all VLANs, the second switch must have VLAN 20 created in its VLAN database for traffic to be forwarded. Without the VLAN existing on the second switch, frames tagged for VLAN 20 are dropped at the receiving switch because there is no corresponding VLAN interface or forwarding table entry.

Answer

The native VLAN is mismatched on the two switches.

Answer

The trunk uses ISL instead of 802.1Q.

Answer

The default gateway is missing for VLAN 20.

Question 19

A company's public web server is experiencing a flood of TCP SYN packets from multiple external IP addresses. The server's connection table is full, causing new legitimate connections to be dropped. Which of the following mitigation techniques should be implemented to protect the server while still allowing legitimate traffic?

Accepted Answer

Implement SYN cookies on the server.. SYN cookies allow the server to avoid storing connection state in the TCP backlog until the three-way handshake completes. When the SYN flood fills the connection table, the server encodes the initial sequence number (ISN) with cryptographic information about the connection, enabling it to verify the ACK from a legitimate client without consuming table entries. This technique preserves resources for legitimate traffic while dropping spoofed or incomplete handshakes.

Answer

Increase the server's TCP connection backlog.

Answer

Enable bogon filtering on the perimeter firewall.

Answer

Deploy an intrusion prevention system (IPS) with signature detection.

Question 20

A network technician is installing a new wireless access point in a warehouse. The AP requires PoE+ (802.3at) for full operation. The technician connects the AP using a Cat5e cable run of 200 feet to a switch that only supports 802.3af (PoE). The AP powers on but has intermittent connectivity issues. What is the most likely cause?

Accepted Answer

The switch does not support the required PoE standard. The switch only supports 802.3af (PoE), which provides up to 15.4W per port, while the AP requires 802.3at (PoE+) for full operation, which supplies up to 30W. Although the AP powers on, it may not receive sufficient power to operate all radios or features, leading to intermittent connectivity issues. The cable length of 200 feet is within the 100-meter (328-foot) limit for Cat5e, so length is not the problem.

Answer

The cable length exceeds the maximum for PoE

Answer

The AP is experiencing interference from metal racks

Answer

The AP is configured with the wrong SSID