Network+ Troubleshooting Practice Questions

What could be a reason for a router failing to receive routing protocol updates?

The router has the lowest administrative distance.

The router is receiving too many ping requests.

There is an authentication issue or incorrect protocol parameter.

The router is configured with static routes only.

There is an authentication issue or incorrect protocol parameter.

A router may fail to receive routing protocol updates due to authentication issues or incorrect protocol parameters, affecting its ability to communicate with neighbors.

Receiving ping requests does not affect routing protocol updates.

Having the lowest administrative distance does not prevent receiving updates.

Even routers configured with static routes can receive dynamic updates unless specifically configured not to.

During a routine security audit, you discover that an unauthorized device is communicating with your network. You decide to manually add a static ARP entry on your Linux server to redirect the traffic from the unauthorized device's IP address to a secure location for further analysis.

Which command would you use to add a static ARP entry for the IP address 192.168.1.100 with the MAC address 00:1A:2B:3C:4D:5E?

arp -a 192.168.1.100 00:1A:2B:3C:4D:5E

ip neigh add 192.168.1.100 lladdr 00:1A:2B:3C:4D:5E nud permanent dev eth0

arp -s 192.168.1.100 00:1A:2B:3C:4D:5E

arp -d 192.168.1.100

ip neigh add 192.168.1.100 lladdr 00:1A:2B:3C:4D:5E nud permanent dev eth0

The ip neigh add 192.168.1.100 lladdr 00:1A:2B:3C:4D:5E nud permanent dev eth0 command is correct. On Linux, the ip neigh command is used to manage the ARP cache, and the correct syntax to add a static ARP entry is ip neigh add followed by the IP address, lladdr for the MAC address, nud permanent to indicate a non-temporary entry, and specifying the network device (e.g., dev eth0).

While the arp -s command is used on Windows to add a static ARP entry, the scenario specifies a Linux server, where the ip neigh command should be used instead.

The arp -a command is used to view the ARP cache, not to add or modify entries.

The arp -d command is used to delete an ARP entry. This action would not help in redirecting the traffic from the unauthorized device as intended in the scenario.

What role does the Spanning Tree Protocol (STP) play in preventing network issues?

It increases network speed.

It prevents switching loops.

It manages bandwidth allocation.

It encrypts data transfers.

It prevents switching loops.

The Spanning Tree Protocol (STP) is designed to prevent switching loops within a network. Switching loops occur when there are multiple paths between switches that can cause broadcast frames to circulate indefinitely, leading to broadcast storms and network failures. STP creates a loop-free logical network topology by blocking redundant paths, ensuring that data frames do not loop endlessly. This prevention of switching loops is crucial for maintaining network stability and performance.

STP's primary function is not to increase network speed but to prevent switching loops that can degrade network performance.

While securing data transfers is important, STP's role is focused on preventing switching loops, not on encrypting data or enhancing data transfer security.

Managing bandwidth allocation involves controlling how network resources are distributed among users and services. STP does not manage bandwidth allocation but prevents switching loops to ensure network stability.

A network administrator at a large office notices that employees in the marketing department frequently complain about dropped video calls as they move between conference rooms. The office is equipped with multiple access points (APs) to ensure coverage.

After some investigation, the administrator realizes that the employees' devices are not smoothly transitioning between APs.

Which of the following actions should the administrator take to improve the roaming experience for these employees?

Implement 802.11r (Fast BSS Transition) on the network to assist with quicker reauthentication.

Replace all 2.4 GHz APs with 5 GHz APs to increase the speed of the connections.

Decrease the signal strength of all access points to encourage devices to switch more frequently.

Increase the security encryption level on all APs to ensure a more stable connection.

Implement 802.11r (Fast BSS Transition) on the network to assist with quicker reauthentication.

Implementing 802.11r, or Fast BSS Transition, on the network can significantly improve the roaming experience by making the reauthentication process faster and more seamless as devices move between APs. This is beneficial in environments where users move around frequently during activities that require stable connections, such as video calls.

Decreasing the signal strength of all APs could lead to coverage gaps and worsen the problem

Replacing 2.4 GHz APs with 5 GHz APs might increase speed but doesn’t create smooth transitions between APs. 5 GHz signals have a shorter range, which could create coverage issues.

Increasing the security encryption level improves security but does not directly impact the smoothness of roaming transitions.

How does IEEE 802.1p work in conjunction with VLANs for traffic management?

By encrypting data traffic

By prioritizing internet access

By segregating voice and data traffic into different VLANs

By assigning IP addresses to devices

By segregating voice and data traffic into different VLANs

IEEE 802.1p often works in conjunction with VLANs to manage traffic on local networks. I.E, voice traffic can be allocated to a different VLAN than data traffic, allowing for more effective prioritization and management of different types of network traffic.

IEEE 802.1p and VLANs are used for traffic management and prioritization, not for encrypting data traffic.

Prioritizing internet access is not the primary function of IEEE 802.1p in conjunction with VLANs;

Assigning IP addresses to devices is a function of DHCP.

During a routine inspection of a fiber optic network that services a critical communications infrastructure, you discover that some sections of the network are experiencing higher than normal signal attenuation. You need to quickly identify whether the issue is due to dirty connectors or actual damage to the fiber.

Which tool would be most effective for initially diagnosing the problem?

Spectrum Analyzer

Cable Certifier

Visual Fault Locator (VFL)

Fusion Splicer

Visual Fault Locator (VFL)

A Visual Fault Locator (VFL) is a practical tool for quickly identifying breaks, bends, and major issues in fiber optic cables, as well as problems with connectors. It can help determine whether the attenuation is due to dirty connectors (by identifying no faults in the cable itself) or if there is visible damage to the fiber that needs further investigation.

A fusion splicer is used for joining two fiber strands together, not for diagnosing or identifying issues such as dirty connectors or damage.

A spectrum analyzer is used to analyze the frequency spectrum of electrical signals, not for direct inspection or diagnosis of physical issues in fiber optic networks.

Cable certifiers are primarily used for certifying the performance of copper and, in some cases, fiber optic cabling to industry standards, but they are not the best tool for quickly diagnosing the specific cause of signal attenuation like a VFL.

What are the broad categories of issues in wireless troubleshooting? (Select two)

Network layer issues

Software issues

Privacy issues

Configuration issues

Hardware issues

Security issues

Physical layer issues

Application layer issues

Configuration issues and physical layer issues.

Wireless troubleshooting primarily focuses on resolving issues related to the physical layer, such as signal strength or interference, and configuration issues, which include incorrect settings for security and authentication. These two categories encompass the most common problems encountered in wireless networks.

You are the lead network engineer responsible for maintaining the network infrastructure of a large enterprise. One day, you receive reports that a specific department is experiencing intermittent network connectivity issues. This problem affects various applications and services, including email, web browsing, and internal database access. After a preliminary investigation, you find no issues with the network hardware or server configurations.

Given the intermittent nature of the problem and its impact on multiple services, you decide to employ the divide and conquer approach of the OSI model to efficiently troubleshoot and identify the root cause of the connectivity issues. Which of the following steps should you take first to troubleshoot the intermittent network connectivity issues?

Inspect the configuration of the routers and switches to ensure they are correctly routing and switching packets.

Analyze the session management to ensure that connections between the client and server applications are stable.

Check the application logs on the affected workstations and servers for any errors or warnings.

Examine the network cables and connections for any signs of damage or improper connection.

Inspect the configuration of the routers and switches to ensure they are correctly routing and switching packets.

Inspecting the configuration of the routers and switches to ensure they are correctly routing and switching packets (Layer 3) is the correct answer. The divide and conquer approach involves starting the troubleshooting process at the layer most likely to be causing the problem, based on the symptoms and preliminary information. Given the intermittent nature of the connectivity issues affecting multiple services, it suggests a potential problem with how data is being routed or switched within the network. Layer 3 (Network Layer) is responsible for packet forwarding, including routing through different routers. Starting the investigation at this layer is logical because it can quickly identify if misconfigurations or issues in routing and switching are causing the intermittent connectivity problems.

What happens if a MAC address cannot be found in the MAC address table?

The switch transmits the frame out of all ports, except for the source port.

The switch discards the frame.

The switch sends the frame to a default port.

The switch requests the MAC address from a central database.

The switch transmits the frame out of all ports, except for the source port.

If a MAC address is not found in the MAC address table, the switch will flood the frame out of all ports except the one it was received on. This behavior is known as flooding and is a way to ensure the frame reaches its intended destination even if the address is not currently known.

Options B, C, and D are incorrect because discarding the frame, sending it to a default port, or requesting the MAC address from a database are not standard behaviors of a switch in this scenario.

During a routine security audit of a corporate wireless network, an IT security specialist discovers several instances of unexpected client disassociations in the network logs. There is no evidence of roaming, interference, or compatibility issues with roaming standards. What should be the specialist's next step to address the potential security concern?

Recommend switching all wireless communication to the 2.4 GHz band for increased range.

Increase the transmit power of all access points to ensure a stronger signal.

Advise all users to update the firmware on their wireless devices immediately.

Investigate the possibility of a disassociation or deauthentication attack on the network.

Investigate the possibility of a disassociation or deauthentication attack on the network.

Given the lack of common issues like roaming, interference, or standards compatibility, the unexpected disassociations could indicate a security threat, such as a disassociation or deauthentication attack. These attacks involve sending spoofed frames to disconnect legitimate clients from the network. Investigating this possibility is crucial for maintaining network security and integrity.

What is the main difference between screened cabling and fully shielded cabling?

Screened cabling uses a braided outer screen only.

Fully shielded cabling uses foil-shielded pairs without an outer shield.

Screened cabling has one thin outer foil shield around all pairs.

Fully shielded cabling has no shielding at all.

Screened cabling has one thin outer foil shield around all pairs.

Screened cabling, often designated as screened twisted pair (ScTP) or foiled/unshielded twisted pair (F/UTP), features a single thin outer foil shield that encompasses all wire pairs within the cable. This design helps to protect against electromagnetic interference from external sources, providing a moderate level of shielding while maintaining flexibility and ease of installation.

During a network upgrade, a network administrator replaces several old switches with new ones that support jumbo frames. After the upgrade, the administrator observes an increase in the number of giant frame errors on interfaces connected to a storage area network (SAN). What is the MOST likely reason for these errors?

The MTU settings on the SAN devices do not match the switch configuration.

The network cables connecting the SAN to the switches are of poor quality.

The new switches are incompatible with the SAN devices.

The SAN devices are using outdated firmware.

The MTU settings on the SAN devices do not match the switch configuration.

The most likely reason for an increase in giant frame errors after upgrading to switches that support jumbo frames is that the MTU settings on the SAN devices do not match the new switch configuration. If the switches are configured to support jumbo frames but the SAN devices are not configured with a matching MTU size, the frames sent by the SAN could be considered too large by the switches, resulting in giant frame errors.

A network administrator suspects that an unauthorized web server is running on one of the company's internal machines. The administrator wants to quickly check for any services listening on common web server ports across the network. Which netstat command should the network administrator use to identify listening ports?

netstat -a

netstat -o

netstat -s

netstat -n

netstat -a

The -a switch with netstat displays all connections and listening ports, making it the best choice for the network administrator to identify any unauthorized web servers by checking for listening ports on common web server ports (e.g., 80, 443).

What is the purpose of caching ARP results?

To increase the encryption level of data packets

To assign static IP addresses to devices

To increase the speed of the routing process

To reduce the amount of ARP traffic on the network

To reduce the amount of ARP traffic on the network

The correct answer is to reduce the amount of ARP traffic on the network. By caching ARP results, devices can minimize the frequency of ARP broadcasts, reducing unnecessary network traffic and improving overall network performance.

ARP caching primarily affects local communication efficiency, not the routing process across networks.

In a switched environment, under which condition are runt frame errors and collisions most likely to occur?

When all devices are configured with the same MTU size

When high-quality cables are used throughout the network

When all switch ports are configured for full-duplex mode

When a legacy hub device is connected to a switch and there is a duplex mismatch

When a legacy hub device is connected to a switch and there is a duplex mismatch

The correct answer is when a legacy hub device is connected to a switch and there is a duplex mismatch. Runt frame errors and collisions are most likely to occur in a switched environment when a legacy hub device is connected to a switch and there is a duplex mismatch. This setup can lead to collisions because hubs operate in half-duplex, causing devices to transmit simultaneously, resulting in collisions and consequently runt frames. Duplex mismatches exacerbate this issue by further disrupting the normal flow of traffic.

A network engineer is tasked with optimizing the network performance of a Linux-based server. The engineer suspects that there are unnecessary services running that could be consuming network resources.

The network engineer wants to identify all services that are currently listening for incoming connections so they can review and potentially disable any that are not required.

Which netstat command should the network engineer use to identify these services?

netstat -p

netstat -l

netstat -s

netstat -at

netstat -l

The -l switch with netstat lists only ports in the listening state, which is exactly what the network engineer needs to identify services that are waiting for incoming connections. This command will help the engineer pinpoint potential candidates for optimization by revealing services that may not be necessary for the server's operation.

What is the first step in diagnosing VLAN assignment issues using ping?

Ping the loopback address, then the host's own IP address.

Ping the default gateway.

Ping a remote host or server.

Ping another host on the same VLAN/subnet.

Ping the loopback address, then the host's own IP address.

Pinging the loopback address and then the host's own IP address is the first step to verify that TCP/IP is functioning correctly and the host's IP configuration is appropriate.

As part of a network optimization project, you are analyzing the traffic generated by various protocols on your company's network. You notice that the discovery protocol in use is generating updates too frequently, causing unnecessary network traffic. You recall that the protocol currently in use sends updates every 30 seconds by default.

You decide to switch to a protocol that reduces the frequency of these updates. Which protocol should you switch to?

Cisco Discovery Protocol (CDP)

Dynamic Host Configuration Protocol (DHCP)

Network Time Protocol (NTP)

IEEE Link Layer Discovery Protocol (LLDP)

Cisco Discovery Protocol (CDP)

The correct answer is Cisco Discovery Protocol (CDP). Since the protocol currently in use sends updates every 30 seconds by default (which is the default interval for LLDP), switching to CDP, which sends updates every 60 seconds by default, would reduce the frequency of the updates and potentially alleviate the network congestion.

What can 802.11k transmit to mitigate sticky and flapping client issues?

The number of clients connected to each AP

Encryption keys for secure communication

Information about the wireless topology

Passwords for network security

Information about the wireless topology

802.11k can transmit information about the wireless network's topology to the client. This helps clients make more informed decisions about when to roam and which AP to connect to, mitigating sticky and flapping client issues.

A small office is planning to install several IP cameras for security purposes. The IT manager wants to ensure a clean setup without running separate power lines for each camera. The office network includes a switch that supports the IEEE 802.3at (PoE+) standard.

Which of the following is the most appropriate solution for powering the IP cameras?

Use a power injector for each IP camera.

Install separate AC adapters for each IP camera.

Use standard Ethernet cables to connect the IP cameras to the PoE+ switch.

Replace the existing switch with one that supports the IEEE 802.11ac standard.

Use standard Ethernet cables to connect the IP cameras to the PoE+ switch.

The IEEE 802.3at (PoE+) standard supports up to 30 W of power, which is sufficient for most IP cameras. By using a PoE+ switch and standard Ethernet cables, the office can power the cameras over the same cables used for data transmission, ensuring a clean setup without the need for separate power lines.

A power injector would only be necessary if the switch did not support PoE. Since the switch supports the IEEE 802.3at (PoE+) standard, it can directly power the IP cameras without additional equipment.

A network administrator is tasked with troubleshooting intermittent network issues that have been reported by users in their organization. The administrator decides to use a packet sniffer to capture network traffic for analysis.

Given the need to capture all traffic, including potentially corrupt or malformed frames, which connection method should the network administrator use to ensure comprehensive data capture?

Use SPAN/port mirroring on a network switch.

Directly connect the sniffer to the internet router.

Install a Passive TAP between the network segments.

Configure an Active TAP with signal regeneration.

Install a Passive TAP between the network segments.

A Passive TAP is the best choice because it physically copies all the traffic, including corrupt or malformed frames, without affecting the original data flow. This ensures a comprehensive capture of all network traffic, which is crucial for troubleshooting the intermittent issues reported.

A corporate office has deployed a wireless network with multiple APs to ensure complete coverage. Employees have been experiencing issues where their devices remain connected to an AP with a weak signal even when they move closer to another AP with a stronger signal. What strategy could the IT department employ to address this issue of "sticky clients"?

Enable load balancing on the APs to distribute clients more evenly across the network.

Implement a band steering technology to push devices from the 2.4 GHz band to the 5 GHz band.

Configure 802.11k and 802.11v standards on the network to provide better information to clients about the network environment.

Decrease the density of APs to reduce the number of available connections.

Configure 802.11k and 802.11v standards on the network to provide better information to clients about the network environment.

The issue described is typical of "sticky clients," which fail to switch to a closer AP with a stronger signal due to lack of information or poor decision-making algorithms. Implementing 802.11k (Radio Resource Measurement) and 802.11v (Wireless Network Management) can help by providing clients with information about the network topology and suggesting when to switch to a better AP, thus mitigating the sticky client issue.

Load balancing distributes clients across APs to prevent any single AP from being overloaded but does not directly encourage sticky clients to switch to a closer AP with a stronger signal.

What is the default multicast address used by Cisco Discovery Protocol (CDP)?

01:80:c2:00:00:0e

00:00:0c:cc:cc:cd

FF:FF:FF:FF:FF:FF

01:00:0c:cc:cc:cc

01:00:0c:cc:cc:cc

CDP uses the multicast address 01:00:0c:cc:cc:cc to send status announcements over local interfaces. This address is specific to CDP and allows Cisco devices to recognize CDP packets.

01:80:c2:00:00:0e is the multicast address used by the IEEE Link Layer Discovery Protocol (LLDP), not CDP.

FF:FF:FF:FF:FF:FF is the broadcast address used in Ethernet networks for broadcasting to all devices, not specific to CDP.

00:00:0c:cc:cc:cd is not a recognized multicast address for CDP or any standard discovery protocols.

A system administrator is troubleshooting a complex network issue that involves routing through multiple subnets and domains. To simplify the analysis and focus solely on the IP addresses and the path that packets take, the administrator decides to use the tracert command on a Windows system.

Given that the system administrator wants to avoid the additional overhead and potential confusion of resolving IP addresses to hostnames during this diagnostic process, which tracert command option should the administrator use to ensure the output is limited to IP addresses only?

tracert -d

tracert -I

tracert -6

tracert -w

tracert -d

The tracert -d command option disables DNS resolution, causing the tracert output to display only IP addresses without attempting to resolve them to hostnames. This option is particularly useful for network diagnostics where the focus is on the routing path and IP addresses, avoiding the delays and potential distractions associated with hostname resolution.

The tracert -I (capital i) command is incorrect because this option is not valid for the tracert command on Windows systems. The -I option is associated with the traceroute command on other systems for specifying ICMP Echo Request probes, and it does not relate to disabling DNS resolution.