N10-009 Network Troubleshooting Practice Test 7 — 15 Questions

Question 1

A user reports that they cannot access a web server at 10.0.1.200. The user can ping the server's IP address but cannot open the web page. The web server is known to be running and accessible from other users on the same subnet. What is the most likely cause?

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

Accepted Answer

ACL blocking port 80 or 443. The user can ping the server (ICMP works) but cannot access the web page, which indicates Layer 3 connectivity is fine but the specific TCP ports (80 for HTTP or 443 for HTTPS) are being blocked. An ACL applied on the server, a switch, or a router between the user and the server is the most likely cause, as it would permit ICMP echo requests while denying HTTP/HTTPS traffic. Other users on the same subnet can access the server, ruling out server-side or subnet-wide issues.

Answer

Default gateway is misconfigured

Answer

DNS resolution failure

Answer

Duplicate IP address

Question 2

A network technician is troubleshooting an intermittent connectivity issue between two switches connected via fiber optic cable. The link status shows up/down flapping. The technician checks the optical power levels and finds they are within acceptable range. Which of the following is the most likely cause?

Accepted Answer

Dirty fiber connectors. Dirty fiber connectors cause intermittent connectivity by scattering or absorbing light, leading to bit errors and link flaps even when average optical power levels appear within acceptable range. The flapping occurs because transient contaminants (e.g., dust or oil) momentarily disrupt the optical signal, triggering link down events that recover when the connector is jostled or the contaminant shifts. Since the power meter measures average power, it may not detect brief attenuation spikes caused by dirt.

Answer

Electromagnetic interference

Answer

Incorrect VLAN configuration

Answer

Duplex mismatch

Question 3

Users in VLAN 10 cannot obtain IP addresses from a DHCP server located in VLAN 20. The router has an ip helper-address configured on VLAN 10 interface pointing to the DHCP server. Users can ping the DHCP server IP from the router. However, users are receiving APIPA addresses. What is the most likely cause?

Accepted Answer

The DHCP server scope does not include the VLAN 10 subnet. The DHCP server must have a scope configured for the subnet of the requesting clients (VLAN 10) to assign IP addresses from that range. Since users receive APIPA addresses (169.254.x.x), the DHCP discovery process is failing, which typically occurs when the server receives the request via the ip helper-address but has no matching scope for VLAN 10. The router's ability to ping the server confirms Layer 3 reachability, isolating the issue to the server's scope configuration.

Answer

The DHCP server is not reachable from the router

Answer

The router's ip helper-address is configured incorrectly

Answer

The switch ports are not configured for VLAN 10

Question 4

A user reports that they cannot access a web server by its URL but can access it by IP address. A technician checks the DNS server and finds it is reachable. What is the most likely cause?

Accepted Answer

DNS resolution failure for that specific record. The user can access the web server by IP address but not by URL, which indicates that the name-to-IP resolution is failing. Since the DNS server is reachable, the issue is not with network connectivity to the DNS server but rather with the specific DNS record for that web server. This is a classic DNS resolution failure for that specific record, often due to a missing or incorrect A or AAAA record.

Answer

Incorrect default gateway

Answer

Firewall blocking port 80

Answer

IP conflict on the user's workstation

Question 5

A technician is troubleshooting an intermittent connectivity issue between two switches connected by a fiber optic cable. The link status shows up/down flapping. The technician checks the optical power levels and finds they are within acceptable range. Which of the following is the most likely cause?

Accepted Answer

Dirty fiber connectors. Intermittent link flapping with acceptable optical power levels strongly indicates a physical-layer issue that is not related to signal strength. Dirty fiber connectors cause intermittent signal degradation due to scattering and absorption of light, leading to CRC errors and link flaps even when average power appears normal. Cleaning the connectors is the standard first step in such scenarios.

Answer

Duplex mismatch

Answer

Speed mismatch

Answer

VLAN mismatch

Question 6

Users in a branch office report intermittent connectivity to the corporate data center. A technician runs a continuous ping from a workstation to the data center server and observes packet loss after the third hop. Which command should the technician run next to identify the specific router causing the issue?

Accepted Answer

tracert server_ip. The technician has already identified packet loss after the third hop using a continuous ping. The next logical step is to use `tracert` (or `traceroute` on Linux) to map the path and pinpoint which router (hop) is dropping packets. This command sends ICMP echo requests with incrementing TTL values, forcing each router along the path to reply with a Time Exceeded message, thereby revealing the specific hop where loss occurs.

Answer

ping -n 1000 server_ip

Answer

nslookup server_ip

Answer

ipconfig /all

Question 7

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 8

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.

Answer

Duplex mismatch

Answer

Incorrect MTU

Answer

Route flapping

Question 9

A user reports that they cannot access any network resources. The technician checks the IP configuration and sees that the workstation has an IP address of 169.254.1.5. What is the most likely cause?

Accepted Answer

The DHCP server is unavailable. The IP address 169.254.1.5 is an Automatic Private IP Addressing (APIPA) address (169.254.0.0/16 range), which Windows assigns when a DHCP client fails to receive a lease from a DHCP server. Since the workstation cannot obtain a valid IP configuration, it cannot communicate with any network resources, confirming that the DHCP server is unavailable.

Answer

The DNS server is down

Answer

The default gateway is incorrect

Answer

The subnet mask is mismatched

Question 10

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.

Question 11

A technician is troubleshooting intermittent wireless connectivity in a conference room. A site survey shows strong signal strength but many nearby access points are using channels that overlap with the channel used by the conference room AP. Which of the following is the most likely cause of the issue?

Accepted Answer

Adjacent channel interference from access points on overlapping channels.. The site survey shows strong signal strength but many nearby access points are using channels that overlap with the channel used by the conference room AP. This directly indicates adjacent-channel interference (ACI), where overlapping channels (e.g., channels 1, 2, 3, 4, and 5 all overlap with channel 1 in the 2.4 GHz band) cause contention and retransmissions, degrading performance even with strong signal. ACI is the most likely cause because the overlapping channels create co-existence issues without being on the exact same channel.

Answer

Multipath interference from reflective surfaces.

Answer

Co-channel interference from access points on the same channel.

Answer

Signal attenuation due to distance from the AP.

Question 12

Drag and drop the steps to set up a wireless network with WPA2-PSK encryption on a SOHO router into the correct order.

Accepted Answer

Connect router to modem and power, connect computer via Ethernet, access web interface, configure SSID, select WPA2-PSK and enter passphrase, save settings.. Wireless setup includes hardware connection, web access, SSID, security, and save.

Answer

Connect router to modem and power, access web interface, configure SSID, select WPA2-PSK and enter passphrase, connect computer via Ethernet, save settings.

Answer

Connect computer via Ethernet, access web interface, select WPA2-PSK and enter passphrase, configure SSID, save settings, connect router to modem and power.

Answer

Connect router to modem and power, connect computer via Ethernet, access web interface, save settings, configure SSID, select WPA2-PSK.

Question 13

Drag and drop the steps to configure a firewall rule allowing inbound HTTPS traffic to a web server into the correct order.

Accepted Answer

Define rule name & description, then specify protocol and port (TCP/443), then specify source and destination addresses, then set action to allow and apply the rule.. The correct sequence for configuring a firewall rule to allow inbound HTTPS traffic is to start with a descriptive rule name, then specify the protocol (TCP) and port (443) to identify the service, then define the source and destination IP addresses, and finally set the action to allow and apply the rule. This order follows logical firewall policy design: identification, service definition, addressing, and enforcement. Common mistakes include placing the protocol/port after addressing or delaying the rule name, which can lead to disorganized or incorrect firewall configurations.

Answer

Specify protocol and port (TCP/443), then define rule name & description, then specify source and destination addresses, then set action to allow and apply the rule.

Answer

Specify source and destination addresses, then specify protocol and port (TCP/443), then define rule name & description, then set action to allow and apply the rule.

Answer

Define rule name & description, then specify source and destination addresses, then specify protocol and port (TCP/443), then set action to allow and apply the rule.

Question 14

Match each wireless standard to its maximum theoretical speed.

Accepted Answer

802.11b: Maximum speed of 11 Mbps. Common Wi-Fi standards: 802.11b (11 Mbps), 802.11g (54 Mbps), 802.11ac (1.3 Gbps). Note that 802.11a also runs at 54 Mbps, and 802.11n at up to 600 Mbps.

Answer

802.11a: Maximum speed of 11 Mbps

Answer

802.11n: Maximum speed of 54 Mbps

Question 15

A network technician receives reports that users on the third floor cannot reach the file server at 172.16.5.10, while users on other floors are unaffected. The technician suspects an issue with the access switch on that floor. Which two commands should the technician use to verify the switch's interface status and VLAN configuration? (Choose two.)

Accepted Answer

show interfaces status. The correct commands are show interfaces status and show vlan brief. These directly address the likely causes: a port being down or a VLAN misconfiguration on the third-floor switch. Other commands like show ip route, show arp, and show running-config are less targeted for verifying interface and VLAN status on a Layer 2 access switch.

Answer

show running-config

Answer

show arp

Answer

show ip route