N10-009 Practice Exam 3 — 20 Questions

Question 1

A network engineer is designing a new IPv6 addressing scheme. The company has been assigned a /48 prefix and needs to support up to 250 subnets. Which subnet size should be used to minimize waste while meeting the requirement?

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

Accepted Answer

/56. A /56 subnet provides 256 subnets (2^(56-48) = 2^8 = 256), which meets the requirement of up to 250 subnets with minimal waste. A /48 prefix is the site-level allocation, and using a /56 subnet mask leaves 8 bits for subnetting, offering exactly the needed capacity without over-allocating address space.

Answer

/52

Answer

/64

Answer

/60

Question 2

A network administrator configures a router to send syslog messages to a central log server. The administrator can ping the server from the router, but the server is not receiving any logs. What is the most likely cause?

Accepted Answer

UDP port 514 is blocked between the router and the server. Syslog messages are sent via UDP port 514 by default. Since the administrator can ping the server (ICMP works), but no logs arrive, the most likely cause is that a firewall or ACL is blocking UDP port 514 between the router and the server. This is a classic connectivity issue where Layer 3 reachability exists but the specific transport-layer port is filtered.

Answer

The syslog server is using the wrong protocol (TCP instead of UDP)

Answer

The syslog service on the server is not running

Answer

The router's clock is not synchronized with the server

Question 3

A network administrator is designing a small office network with 40 workstations. The design must ensure that a single cable failure only affects the connected workstation. Which logical topology should the administrator implement?

Accepted Answer

Star. A star topology connects each workstation directly to a central switch or hub, so a cable failure only affects the single connected workstation, not the rest of the network. This meets the requirement for fault isolation at the workstation level, which is the core design goal in a small office with 40 devices.

Answer

Ring

Answer

Bus

Answer

Mesh

Question 4

A network administrator is configuring Quality of Service (QoS) on a router to prioritize voice traffic. Which of the following fields should be used to mark packets for classification and prioritization?

Accepted Answer

DSCP. DSCP (Differentiated Services Code Point) is the correct field because it is a 6-bit value in the IP header used to mark packets for QoS classification and prioritization, as defined in RFC 2474. Voice traffic typically uses DSCP EF (Expedited Forwarding, value 46) to ensure low latency and jitter, making it the standard choice for QoS marking on routers.

Answer

Source IP address

Answer

Source port number

Answer

MAC address

Question 5

A network administrator is configuring a monitoring system to collect metrics from network devices. The administrator needs to ensure that the monitoring system can automatically discover the devices and obtain detailed information about their configuration and status, such as interface descriptions and software versions. Which protocol is best suited for this purpose?

Accepted Answer

SNMP. SNMP (Simple Network Management Protocol) is the correct choice because it is specifically designed for network management and monitoring. It allows a management system to automatically discover devices (via SNMP walks or queries to MIBs) and retrieve detailed configuration and status information, such as interface descriptions and software versions, by reading OIDs from the device's MIB. This matches the requirement for automatic discovery and detailed data collection.

Answer

LLDP

Answer

NetFlow

Answer

Syslog

Question 6

A network administrator wants to prevent unauthorized devices from being plugged into switch ports. Only devices with specific MAC addresses should be allowed on each port. Which switch security feature should be enabled?

Accepted Answer

Port security. Port security is the correct feature because it allows the administrator to restrict which MAC addresses can communicate through a switch port. By configuring allowed MAC addresses (sticky or static), any device with an unknown MAC address attempting to send traffic will trigger a security violation (shutdown, restrict, or protect). This directly addresses the requirement to prevent unauthorized devices from being plugged into switch ports.

Answer

DHCP snooping

Answer

Dynamic ARP inspection

Answer

802.1X

Question 7

Two routers are configured with OSPF in the same area, but they do not form an adjacency. Router A shows OSPF state EXSTART, and Router B shows state EXSTART. Which of the following is the most likely cause?

Accepted Answer

The MTU is mismatched between the two routers. When OSPF routers are stuck in the EXSTART state, it indicates that they have progressed past the 2-Way and ExStart phases but are unable to exchange Database Description (DBD) packets. The most common cause is an MTU mismatch, because OSPF will not proceed to the Exchange state if a DBD packet exceeds the interface MTU of the neighbor. This causes the routers to continuously renegotiate the master/slave relationship without completing the exchange.

Answer

The OSPF Hello and Dead intervals are mismatched

Answer

The OSPF area IDs are different

Answer

The network type is misconfigured (e.g., one side is broadcast, the other is point-to-point)

Question 8

A network administrator needs to power IP phones and wireless access points through the Ethernet cable. Which standard should be supported?

Accepted Answer

802.3af. The 802.3af standard, also known as Power over Ethernet (PoE), delivers up to 15.4 watts of DC power over twisted-pair Ethernet cabling. This allows devices like IP phones and wireless access points to receive both data and power through a single Ethernet cable, eliminating the need for separate power supplies.

Answer

802.11ac

Answer

802.1X

Answer

802.3ab

Question 9

A network administrator wants to prevent rogue DHCP servers from offering IP addresses to clients on the network. Which security feature should be enabled on the switches?

Accepted Answer

DHCP snooping. DHCP snooping is the correct security feature because it acts as a firewall between untrusted hosts and trusted DHCP servers. It validates DHCP messages by filtering out responses from unauthorized DHCP servers on untrusted ports, preventing rogue servers from offering IP addresses to clients. This is achieved by building and maintaining a DHCP snooping binding database that tracks valid IP-to-MAC address mappings.

Answer

Dynamic ARP Inspection (DAI)

Answer

Port Security

Answer

IP Source Guard

Question 10

A security administrator discovers that an attacker has intercepted data between two legitimate hosts by redirecting traffic through a rogue device. Which type of attack is this?

Accepted Answer

Man-in-the-middle. This is a classic man-in-the-middle (MITM) attack, where the attacker intercepts and potentially alters communication between two legitimate hosts by inserting a rogue device into the data path. The key characteristic is the redirection of traffic through the attacker's device, which allows them to capture, inspect, or modify packets in transit.

Answer

ARP poisoning

Answer

DNS poisoning

Answer

Replay attack

Question 11

A user reports that they cannot access the internet. The technician verifies the workstation has IP address 192.168.1.10 with subnet mask 255.255.255.0 and default gateway 192.168.1.1. The user can ping the default gateway successfully. Other users on the same subnet can access the internet. Which command should the technician run on the workstation to further isolate the issue?

Accepted Answer

netstat -r. The user can ping the default gateway (192.168.1.1), indicating Layer 2 and basic Layer 3 connectivity to the local router. However, other users on the same subnet can access the internet, so the issue is likely with the workstation's routing table. The 'netstat -r' command displays the IP routing table, allowing the technician to check for a missing or incorrect default route (e.g., destination 0.0.0.0 with gateway 192.168.1.1). This isolates whether the workstation knows how to forward traffic beyond the local subnet.

Answer

ipconfig /all

Answer

tracert 8.8.8.8

Answer

nslookup google.com

Question 12

Which of the following best describes a broadcast domain?

Accepted Answer

All devices that can receive a broadcast frame from any other device in the network segment. A broadcast domain is defined as the set of all devices that can receive a broadcast frame (destination MAC FF:FF:FF:FF:FF:FF) sent by any other device within the same network segment. This boundary is typically enforced by Layer 3 devices like routers, which do not forward broadcast frames, whereas Layer 2 switches forward broadcasts out all ports except the receiving port within the same VLAN.

Answer

All devices connected to the same switch

Answer

All devices that share the same IP subnet

Answer

All devices that have the same MAC address prefix

Question 13

A user reports intermittent connectivity issues. The technician runs ping tests and notices that pings to the default gateway sometimes fail and sometimes succeed. While pinging, the technician observes that some replies have high latency. Which tool should the technician use to analyze the path and identify where packets are being delayed?

Accepted Answer

traceroute / tracert. Traceroute (tracert on Windows) is the correct tool because it sends packets with incrementing Time-to-Live (TTL) values to map the entire Layer 3 path from source to destination. By measuring the round-trip time (RTT) for each hop, it can pinpoint exactly which router or link is introducing high latency or packet loss, addressing the intermittent connectivity and delayed replies observed in the ping tests.

Answer

nslookup

Answer

ipconfig

Answer

arp

Question 14

A security analyst notices that the network has been flooded with packets that have the same source IP address as the company's internal DNS server. This is likely an example of which type of attack?

Accepted Answer

IP spoofing. IP spoofing is the correct answer because the attacker is forging the source IP address of packets to impersonate the company's internal DNS server. By flooding the network with packets that appear to originate from a trusted internal server, the attacker can bypass security controls, launch reflection attacks, or cause denial of service. This directly matches the scenario where the source IP is falsified to match a legitimate internal host.

Answer

Smurf attack

Answer

Man-in-the-middle

Answer

ARP poisoning

Question 15

A company is implementing a DMZ to host public-facing web and email servers. The DMZ network uses private IP addresses, and the internal network also uses private IP addresses. The company has only one public IP address assigned to the border router's external interface. Which of the following should be configured to allow internet users to access the DMZ servers?

Accepted Answer

Port forwarding to the private IP addresses of the servers.. Port forwarding (often configured as static NAT with a single public IP) allows the border router to forward incoming traffic on specific TCP/UDP ports (e.g., 80 for web, 25 for SMTP) to the private IP addresses of the DMZ servers. Since the company has only one public IP, this is the only way to direct external requests to the correct internal server without requiring multiple public IPs.

Answer

NAT with overload to translate multiple internal addresses to the single public IP.

Answer

Static NAT mapping each DMZ server to a unique public IP.

Answer

A VPN tunnel between the DMZ and the internal network.

Question 16

A network administrator is installing cable in a plenum space (an area used for air circulation, such as above a drop ceiling). Which cable type is required by most building codes for such an installation?

Accepted Answer

Plenum-rated cable. Plenum-rated cable is required by most building codes (e.g., NFPA 70, National Electrical Code) for installation in plenum spaces because it is constructed with fire-retardant materials, such as FEP or PFA, that produce minimal smoke and are self-extinguishing. This prevents toxic fumes and flames from spreading through air-handling areas, ensuring safety in case of a fire. Standard PVC-jacketed cable would release hazardous smoke and support flame propagation, making it illegal in plenum spaces.

Answer

PVC-jacketed cable

Answer

Riser-rated cable

Answer

Low Smoke Zero Halogen (LSZH) cable

Question 17

A user can ping the default gateway (192.168.1.1) but cannot ping the external IP address 8.8.8.8. Other users on the same subnet can ping 8.8.8.8 without issue. The user's IP configuration is correct: IP 192.168.1.10/24, default gateway 192.168.1.1, DNS 8.8.8.8. What is the most likely cause?

Accepted Answer

The computer's firewall is blocking outbound ICMP. The user can ping the default gateway (192.168.1.1) but not the external IP 8.8.8.8, while other users on the same subnet can ping 8.8.8.8 without issue. This isolates the problem to the user's specific host, not the network infrastructure. A local firewall on the user's computer blocking outbound ICMP (Internet Control Message Protocol) traffic would prevent ping to external IPs while still allowing local subnet communication, as ICMP is often restricted by default in some security policies.

Answer

The router is missing a default route to the internet

Answer

The DNS server is not resolving the hostname

Answer

The network cable is loose or faulty

Question 18

A network engineer is troubleshooting intermittent call drops on a VoIP deployment. The network uses separate VLANs for voice (VLAN 20) and data (VLAN 10). Switch ports connecting the IP phones are configured with the correct voice VLAN. Which of the following is the MOST likely cause to check NEXT?

Accepted Answer

Verify that QoS markings and queuing are configured on the switches and routers. Intermittent call drops on a VoIP deployment with separate voice and data VLANs most likely stem from insufficient or misconfigured QoS markings and queuing. Voice traffic is sensitive to latency, jitter, and packet loss, which occur when data traffic competes for bandwidth without proper prioritization. Verifying that switches and routers have consistent QoS policies (e.g., marking with DSCP EF for RTP and queuing with strict priority) is the logical next step after ensuring the voice VLAN is correctly assigned.

Answer

Check the DNS server for the phone's name resolution

Answer

Replace the patch cables from the phones to the switches

Answer

Increase the DHCP lease time for the phones

Question 19

Which of the following is the primary function of a subnet mask in IPv4 networking?

Accepted Answer

It determines the network portion of an IP address. The subnet mask's primary function is to distinguish the network portion from the host portion of an IPv4 address. By applying a bitwise AND operation between the IP address and the subnet mask, the network address is derived, which is essential for routing decisions. Without this separation, devices cannot determine whether a destination is local or requires forwarding through a router.

Answer

It identifies the default gateway for a subnet

Answer

It provides encryption for data in transit

Answer

It maps IP addresses to MAC addresses

Question 20

Users in a branch office report that file transfers to the data center are slow. A technician runs a traceroute and sees consistently high latency on hop 5. The technician then pings hop 5 and gets replies with varying response times. There are no errors reported on the interface. What is the most likely cause?

Accepted Answer

Interface congestion causing queuing delays.. High latency on hop 5 with varying response times and no interface errors indicates that the router at hop 5 is experiencing congestion, causing packets to be queued before transmission. This queuing delay results in increased and variable round-trip times (RTT), which is a classic symptom of interface congestion. The absence of errors rules out physical-layer issues, and the consistent latency on that specific hop points to a bottleneck at that router's egress interface.

Answer

Routing loop causing packets to be dropped.

Answer

DNS server misconfiguration causing lookup delays.

Answer

Firewall inspecting traffic and adding latency.