LPI 102-500 Practice Test Questions, Exam Dumps

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102-500 LPI Practice Test Questions and Exam Dumps

Question No 1:

Which command is used to change the hostname of the local system in a Linux-based environment?

Answer: hostname

Explanation:

In a Linux-based system, the hostname represents the system's network name, and it is an essential part of the system's identity. The hostname is used to uniquely identify a machine within a network and is a crucial piece of information for networking tasks, such as resolving domain names, establishing network connections, or configuring network services.

Command to Set Hostname:

The correct command to set or change the hostname of the local system is hostname. This command is used without any path or parameters to either view or set the hostname temporarily during the current session. If the system is restarted, the hostname will revert to the default one unless it is configured permanently through other methods (such as editing configuration files).

For example:

To view the current hostname of the system, you can simply type:

hostname

To set a new hostname temporarily (until the next reboot), you can use:

hostname newhostname

Making the Change Permanent:

While the hostname command changes the hostname temporarily, this change is not persistent. To make the change permanent, you need to modify the system configuration files. The exact method may depend on the distribution being used.

On systems using systemd (such as Ubuntu 16.04 and later), you would modify the hostname by running:

sudo hostnamectl set-hostname newhostname

This command updates the hostname permanently, and the change will persist across reboots.
On older systems or systems not using systemd, you would modify the /etc/hostname file directly, replacing the current hostname with the desired one. You would also need to edit the /etc/hosts file to map the new hostname to the system’s IP address.

Explanation of the Command’s Functionality:

Temporary Change: The hostname command changes the hostname only for the current session. After rebooting, the system will revert to its default hostname unless permanent changes are made via other methods.
Permanent Change: For a permanent change, it is necessary to either modify system files (/etc/hostname and /etc/hosts) or use more advanced tools like hostnamectl (on systems that use systemd).

To change the hostname of a Linux-based system temporarily, the hostname command is used. However, if the change needs to persist across system reboots, additional configuration steps (like editing system files or using hostnamectl) are required. This command plays a vital role in managing network identity on Linux systems.

Question No 2:

Which of the following is a valid IPv6 address?

A. 2001:db8:0g21::1
B. 2001::db8:4581::1
C. 2001:db8:3241::1
D. 2001%db8%9990%%1
E. 2001.db8.819f..1

Correct Answer: C. 2001:db8:3241::1

Explanation:

IPv6 (Internet Protocol version 6) is the most recent version of the Internet Protocol (IP) that allows for a much larger address space compared to IPv4. An IPv6 address consists of eight groups of four hexadecimal digits, separated by colons. It can also feature shorthand notations to simplify long strings of zeros, such as the use of "::" to represent one or more groups of consecutive zeros.

To determine which address is valid, let’s review each option:

Explanation of Correct Answer (C):

The address 2001:db8:3241::1 is a valid IPv6 address. Here's why:

It follows the correct format for an IPv6 address, consisting of eight groups of hexadecimal digits, although "::" is used to compress consecutive zero groups.
It is a shorthand representation where "::" represents one or more zero groups.
The address 2001:db8:3241::1 is correctly formatted and adheres to the syntax rules of IPv6.

Why the Other Answers Are Incorrect:

A. 2001:db8:0g21::1: This address is invalid because the group "0g21" contains a letter "g", which is not a valid hexadecimal character. Hexadecimal digits only include the numbers 0-9 and the letters a-f. Therefore, this is not a valid IPv6 address.
B. 2001::db8:4581::1: This address is invalid because it contains multiple shorthand notations for zero groups. In IPv6 addresses, the "::" shorthand can only be used once in an address. Having two instances of "::" leads to ambiguity, making this address invalid.
D. 2001%db8%9990%%1: This address is invalid because it contains percentage signs (%), which are not valid in standard IPv6 notation. The "%" symbol is used in IPv6 link-local addresses to specify the scope, but it is not part of the standard representation of an IPv6 address.
E. 2001.db8.819f..1: This address is invalid because the periods (".") are not used in IPv6 addresses. Periods are common in IPv4 addresses (e.g., 192.168.1.1), but IPv6 addresses should only use colons (":") to separate groups.

The valid IPv6 address in the provided options is 2001:db8:3241::1 (Option C). This address is correctly formatted and follows the proper IPv6 syntax. When dealing with IPv6 addresses, it's important to adhere to the rules for hexadecimal digits, group separators (colons), and proper shorthand usage to avoid invalid configurations.

Question No 3:

What command, when used with the appropriate options, can display open TCP connections, routing tables, and network interface statistics in a Linux system?

Answer: netstat

Explanation:

The netstat command (short for network statistics) is one of the most widely used tools to gather network-related information on Linux and Unix-based systems. It provides a variety of details about network connections, routing tables, interface statistics, and much more. The command can be used to diagnose network issues, view the current state of network connections, and monitor data flowing through network interfaces.

Key Functions of netstat:

The netstat command, depending on the options provided, can display several important types of information related to the system's network configuration and activity. Some of the most commonly used options and their functionalities include:

Open TCP Connections: The netstat command can display the status of open TCP connections, including both incoming and outgoing connections, the local and remote addresses, and the current connection state (e.g., established, listening, etc.). A common command to list open connections is:

netstat -t

This shows all the open TCP connections.

Routing Tables: netstat can also be used to display the system’s routing table, which shows how packets are routed across different network interfaces. The routing table is essential for determining how traffic is directed to various destinations. To view the routing table, you can use:
netstat -r

This will display the kernel’s routing table, which includes the destination network, gateway, interface, and other relevant data.

Network Interface Statistics: netstat provides statistics for each network interface on the system, such as the number of packets received and transmitted, the number of errors, and more. To display these statistics, the following command is used

netstat -i

This will display the statistics of the network interfaces on the system, such as Ethernet interfaces and virtual network devices.

Common Options for netstat:

-a: Show all active connections (both TCP and UDP).
-t: Display only TCP connections.
-u: Display only UDP connections.
-r: Display the routing table.
-i: Display network interface statistics.
-n: Show numerical addresses (IP addresses and port numbers) instead of resolving hostnames.

Alternatives to netstat:

While netstat is an essential tool, it has been deprecated in favor of newer tools such as ss (Socket Statictics) on newer Linux distributions. The ss command provides similar functionality with improved performance. For example, to view open TCP connections using ss, you can use:

ss -t

The netstat command is a powerful and versatile tool for monitoring and troubleshooting network configurations. It is used to display open TCP connections, view routing tables, and gather network interface statistics, making it invaluable for administrators and network engineers when diagnosing network-related issues. Understanding the various options and their usage is crucial for effectively utilizing this command.

Question No 4:

Which command, included in NetworkManager, is a curses-based application that provides easy access to NetworkManager on the command line?

Answer: nmtui

Explanation:

In Linux-based systems that use NetworkManager for network configuration and management, nmtui (NetworkManager Text User Interface) is a curses-based (text-based user interface) application that provides a user-friendly way to manage network connections directly from the command line. It simplifies the task of configuring and managing network settings without needing to manually edit configuration files or use more complex tools.

Overview of nmtui:

nmtui is an intuitive command-line interface for interacting with NetworkManager, which is the default network configuration tool in many modern Linux distributions (such as Fedora, Ubuntu, CentOS, and RHEL). NetworkManager manages both wired and wireless network connections, VPNs, and other networking tasks. While NetworkManager can be managed via the graphical user interface (GUI), nmtui allows users to configure networks in a more accessible, text-based way.

The tool uses curses, which is a library for creating text-based user interfaces, allowing users to navigate and select options using a simple keyboard interface. This is especially useful for administrators who are working on headless servers or systems without a graphical environment.

Key Features of nmtui:

View and Modify Network Connections: nmtui allows users to view existing network connections, modify their settings, and create new connections without having to manually edit configuration files.
Easily Enable/Disable Networks: You can quickly enable or disable network interfaces, switch between wired and wireless connections, or disable a particular connection when needed.
Interactive Menu: The application provides an interactive, menu-driven interface that simplifies the task of selecting and configuring networks. It is easy to navigate and does not require deep knowledge of network settings or command-line options.
Network Profiles: You can create, modify, or delete network profiles for different interfaces (such as Wi-Fi or Ethernet) directly from nmtui.

Usage Example of nmtui:

To use nmtui, simply run the command in the terminal:

nmtui

This will launch the curses-based interface, where you can select various options such as:

Activate a connection
Edit a connection
View system information

The interface uses keyboard navigation, where users can select options by moving the cursor up and down and pressing Enter to confirm selections.

Why nmtui is Useful:

Simplicity: nmtui is much simpler than directly using command-line tools like nmcli (NetworkManager Command Line Interface), especially for users who are not as comfortable with intricate command-line syntax.
Accessibility: It provides an easy and quick way to manage network connections, particularly on systems that do not have a GUI, such as headless servers or systems used over SSH.
Quick Setup: It is particularly useful when administrators need to quickly set up or modify network configurations without dealing with long or complex configuration files.

Alternatives to nmtui:

nmcli: This is the full command-line interface for NetworkManager, which is more powerful and flexible than nmtui, but it requires knowledge of various commands and syntax.
GUI-based NetworkManager: For desktop users, there is a graphical user interface (GUI) that simplifies network management with a point-and-click interface.

The nmtui command is an easy-to-use curses-based application for managing NetworkManager on Linux systems through a text interface. It provides a simple, menu-driven environment for viewing and configuring network settings, making it ideal for systems that lack a graphical user interface or for administrators who prefer working within a terminal environment.

Question No 5:

Which of the following tools, commonly used for DNS debugging, reports not only the response from the name server but also detailed information about the DNS query?

Answer: dig

Explanation:

dig, which stands for Domain Information Groper, is a widely used tool for DNS (Domain Name System) debugging and troubleshooting. It is a command-line utility that allows network administrators and IT professionals to query DNS servers for information about domain names, IP addresses, mail servers, and other types of DNS records.

How dig Works:

When you run a dig command, it sends a DNS query to a name server and provides detailed information about the query's response. Unlike simpler tools like nslookup, which only provide the query result, dig offers comprehensive data including information about the DNS query itself, the time taken to receive the response, the authoritative name servers, and the server’s response to the query.

Features of dig:

Comprehensive Output: The dig tool reports not only the DNS query result (like an IP address for a domain) but also details about the query, such as the query time, the server that handled the query, and additional information related to DNS record types (e.g., A, MX, CNAME, etc.).
Multiple Query Types: With dig, you can query various types of DNS records, such as:

A: Address record, which maps a domain to an IP address.
MX: Mail exchange record, which maps a domain to email servers.
CNAME: Canonical name record, which allows multiple domain names to point to the same server.
NS: Name server record, which indicates authoritative name servers for a domain.

Detailed Query Information: When you run a query with dig, it provides information about the DNS response, such as:

Query time: How long it took for the server to respond.
Server: Which DNS server responded to the query.
Flags: Information about the query, such as whether it was successful, authoritative, or non-authoritative.
Answer section: The actual DNS records returned by the server.

Diagnostic Tool: dig is a powerful tool for diagnosing DNS issues. It helps in understanding why a DNS query might fail, whether it’s due to server misconfiguration, network issues, or a DNS caching problem.

Example Usage of dig:

A simple dig command looks like this:

dig example.com

This will query the default DNS server for information about example.com. The output will include:

The answer section, which shows the response to the query (e.g., IP addresses).
The authority section, which shows the authoritative name servers for the domain.
The additional section, which may include extra information like related DNS records.

You can also query for specific types of records like so:

dig example.com MX

This will query for the mail exchange records for example.com.

Advantages of dig Over Other Tools:

Detailed Output: Unlike tools like hostname or nslookup, which give limited information, dig offers more granular details.
Control Over Queries: dig allows for flexible querying, giving you control over which DNS record types to query for and providing detailed output.
Reliable for Troubleshooting: dig is often used by network engineers and administrators to diagnose DNS issues or verify DNS configurations across multiple servers.

Other Tools:

dnsq: A tool for querying DNS servers, but it does not provide as detailed a breakdown of the query like dig.
hostname: A command used to display or set the system's hostname, not typically used for DNS debugging.
dnslookup: This command is less common, and while it can resolve domain names, it lacks the detailed query insights that dig offers.
zoneinfo: A tool related to zone file information, but not typically used for DNS query debugging.

dig is the most comprehensive and widely used tool for DNS querying and debugging. It not only provides the response from the DNS server but also gives in-depth details about the query itself, making it an essential tool for diagnosing and troubleshooting DNS-related issues.

Question No 6:

Which of the following statements is a valid entry in the /etc/nsswitch.conf file?

A. multi on
B. 192.168.168.4 dns-server
C. namespaces: net mount procs
D. include /etc/nsswitch.d/
E. hosts: files dns

Answer: E. hosts: files dns

Explanation:

The /etc/nsswitch.conf file is a critical configuration file in Linux and UNIX-based operating systems that controls how the system resolves various types of databases, such as hostnames, users, and groups. This file configures the order in which different name service modules are queried to resolve information about a given resource. For example, resolving hostnames may involve looking up the /etc/hosts file first, then querying DNS servers if the hostname isn't found.

Let’s break down the entries provided in the question and explore which one is valid:

Valid Statement:

E. hosts: files dns
This is a valid configuration line in the /etc/nsswitch.conf file. It specifies how the system should resolve hostnames:

files: First, check the local /etc/hosts file for the hostname resolution.
dns: If the hostname isn't found in /etc/hosts, the system will then query DNS servers to resolve the hostname.

This is a common setup where local host entries are checked first, and DNS is used as a fallback.

Explanation of Other Options:

A. multi on
This is not a valid statement for the /etc/nsswitch.conf file. The multi option is not recognized in this context. This might be a misinterpretation of a different configuration or an incorrect entry.

B. 192.168.168.4 dns-server
This is not valid. The /etc/nsswitch.conf file doesn't work with direct IP addresses or hostnames specified in this way. The proper syntax for specifying DNS in the file involves using dns, not an IP address.

C. namespaces: net mount procs
This is also an invalid entry. The namespaces keyword doesn't exist in the context of /etc/nsswitch.conf. This seems to be an incorrect attempt to define multiple types of name resolution services, but it's not in the correct format for this file.

D. include /etc/nsswitch.d/
This is not a valid statement either. The /etc/nsswitch.conf file doesn't support an include directive to include additional files. This type of configuration may be seen in other configuration files, but it's not valid here.

Key Points About /etc/nsswitch.conf:

Databases: The file typically contains entries for databases like passwd, group, hosts, networks, etc.
Modules: Each database is followed by a list of services or modules to query, such as files (for local files), dns (for DNS servers), nis (for Network Information Service), and others.
Order of Resolution: The order in which services are listed dictates the sequence of resolution attempts. The system will query each service in the order specified until it finds a resolution or fails.

For example, a valid entry for resolving hostnames might look like:

hosts: files dns

This means the system will first check the /etc/hosts file and then try DNS if the entry isn't found locally.

In summary, E. hosts: files dns is the correct and valid configuration line in /etc/nsswitch.conf as it properly defines the order for resolving hostnames via local files first, and then DNS. The other options contain incorrect or unsupported configurations for this file.

Question No 7:

Which of the following connection types, as displayed when using the nmcli connection show command, may be found in NetworkManager? (Choose three.)

A. tcp

B. ethernet

C. wifi

D. ipv6

E. bridge

Answer: B. ethernet, C. wifi, E. bridge

Explanation:

NetworkManager is a powerful tool used in Linux-based systems to manage network connections. It provides a unified interface for connecting to different types of network interfaces, whether wired or wireless, and also supports advanced features like bridging. One of the ways to view and manage the connections on a Linux machine is through the nmcli command-line tool. The nmcli connection show command lists all active and available network connections managed by NetworkManager.

Understanding Network Connections in NetworkManager:

When using the nmcli connection show command, you'll see various connection types, each corresponding to different network configurations. Below are the valid connection types available in NetworkManager:

B. ethernet
The ethernet connection type represents a wired connection to the network using an Ethernet interface (typically via an RJ45 cable). It is one of the most common types of network connections for stationary devices like desktops or servers. When you configure an Ethernet connection in NetworkManager, the tool manages the network interface, handles IP addressing, and ensures a stable connection to the network.

C. wifi
The wifi connection type is used for wireless network connections. These are configured to connect to Wi-Fi networks, which are common in laptops, smartphones, and other mobile devices. Using NetworkManager, you can manage Wi-Fi network connections, configure security protocols (such as WPA2), and set preferences like automatic connection to specific networks.

E. bridge
A bridge connection type is used when creating a network bridge. A network bridge allows multiple network interfaces to be connected together, making them behave like a single interface. This is useful for scenarios like virtual machine networking, creating isolated networks, or combining multiple network interfaces into one. A bridge is typically used to connect virtual machines or containers to physical networks.

Incorrect Answers:

A. tcp
tcp is not a valid connection type in NetworkManager. The Transmission Control Protocol (TCP) is a layer in the OSI model used for communication between devices, but it is not something that is directly managed by NetworkManager. It is part of the protocol stack used by applications for reliable communication, and not a connection type that appears in nmcli connection show.

D. ipv6
While IPv6 is a protocol used for assigning IP addresses, it is not considered a separate connection type in NetworkManager. Instead, IPv6 support is typically included within the configuration of other connection types, such as ethernet or wifi. You would configure IPv6 settings within the context of a specific connection, but it isn't shown as an individual connection type in the output of nmcli connection show.

The three valid connection types that can be displayed when running the nmcli connection show command are:

ethernet: For wired network connections.
wifi: For wireless network connections.
bridge: For network bridging configurations.

These connection types represent the primary methods that NetworkManager uses to manage different types of network interfaces, whether wired, wireless, or virtual. tcp and ipv6 are protocols or features, not independent connection types in the context of NetworkManager.

Question No 8:

On a Linux workstation, the route command takes a long time before displaying the routing table. Which of the following issues is most likely causing this delay?

A. The local routing information may be corrupted and must be re-validated using a routing protocol.
B. One of the routers in the routing table is not available, causing the automatic router failure detection mechanism (ARF-D) to wait for a timeout.
C. There may be more than one default router, requiring a default router election to choose one router as the default.
D. The Linux Kernel Routing Daemon (LKRD) is not running and should be started using its init script or systemd unit.
E. DNS resolution may not be working, as the route command by default attempts to resolve router and destination names, potentially resulting in a timeout.

Answer: E. DNS resolution may not be working, as the route command by default attempts to resolve router and destination names, potentially resulting in a timeout.

Explanation:

The route command in Linux is used to display or modify the IP routing table. When it takes a long time to display the routing table, the issue is often related to how the command processes network information, especially when it attempts to resolve names associated with routers or network destinations.

Why DNS Resolution Causes Delay:

The most common cause for a delay when running the route command is a DNS resolution problem. By default, when the route command is run, it attempts to resolve any hostnames in the routing table to IP addresses. If DNS resolution is not functioning correctly or if there is a misconfigured DNS server, the command will hang while waiting for the DNS query to time out. This timeout can significantly delay the display of the routing table.

This issue is particularly noticeable when there are entries in the routing table that involve hostnames instead of IP addresses. Since the route command waits for a DNS resolution (if configured to do so), a slow or failing DNS server will result in a delay.

Explanation of Other Options:

A. The local routing information may be corrupted and must be re-validated using a routing protocol.
While corrupted routing information could potentially cause issues, it wouldn't typically result in a delay when displaying the routing table. The route command is more likely to encounter an issue if it cannot find a route or if the system has a misconfigured network. Corruption would not explain the delay caused by DNS resolution.
B. One of the routers in the routing table is not available, causing the automatic router failure detection mechanism (ARF-D) to wait for a timeout.
Router failure detection mechanisms like ARF-D (if used) would typically be handled by other tools or protocols, such as dynamic routing protocols (e.g., OSPF, BGP) and wouldn't directly affect the route command's behavior. The route command doesn't wait for router failure detection.
C. There may be more than one default router, requiring a default router election to choose one router as the default.
Having multiple default routes would lead to network issues or traffic being sent to the wrong destination, but it would not cause a delay in displaying the routing table. The route command simply displays the routes and does not trigger router election processes.
D. The Linux Kernel Routing Daemon (LKRD) is not running and should be started using its init script or systemd unit.
The Linux Kernel Routing Daemon (LKRD) is not a component of the Linux system. Routing in Linux is handled directly by the kernel and utilities like ip and route. The issue with route not displaying the table would not be related to a non-existent LKR daemon.

The most likely cause of a delay in the route command output is DNS resolution issues. If DNS resolution is not working properly or there is a misconfigured DNS server, the command will attempt to resolve hostnames and may time out, causing a delay in displaying the routing table. This can be confirmed by checking the network configuration and ensuring DNS servers are correctly set up.

Question No 9:

Which of the following subcommands are valid in nmcli, the command-line interface for NetworkManager? (Choose two.)

A. nmcli ethernet
B. nmcli device
C. nmcli wifi
D. nmcli address
E. nmcli connection

Answer:

B. nmcli device
E. nmcli connection

Detailed Explanation:

nmcli is a command-line interface (CLI) tool for managing network connections on Linux-based systems using NetworkManager. NetworkManager is a daemon that provides tools for managing network devices, interfaces, and connections. nmcli is useful for configuring and troubleshooting network settings in a Linux environment without needing a graphical user interface.

Understanding nmcli Subcommands:

The nmcli command uses a set of subcommands to interact with various network-related components. Some subcommands deal with devices, connections, or settings, while others focus on specific network configurations like wireless or VPN settings. Here’s a breakdown of the relevant subcommands in the given options:

nmcli device:

The nmcli device subcommand is used to show the status of network devices on the system, including Ethernet adapters, Wi-Fi interfaces, VPNs, and more. It provides information about the connectivity status, such as whether a device is connected or disconnected, its IP address, and other interface-specific details.

Example command:
nmcli device status

This will list all network devices and their current statuses.

nmcli connection:

The nmcli connection subcommand is used for managing and displaying network connections on a system. A "connection" represents a specific network configuration (such as a Wi-Fi network or VPN).

Example command:
nmcli connection show

This lists all available network connections, showing details like connection type (e.g., wired, wireless), interface name, and current state (connected or disconnected).

Why the Other Options Are Incorrect:

A. nmcli ethernet:
This subcommand is not valid in nmcli. While you can configure Ethernet connections through nmcli, there's no specific subcommand like nmcli ethernet. Ethernet interfaces are managed through the broader nmcli device and nmcli connection commands.
C. nmcli wifi:
While managing Wi-Fi interfaces is possible via nmcli, there is no dedicated nmcli wifi subcommand. Instead, Wi-Fi settings can be configured using the nmcli device wifi or nmcli connection commands.
D. nmcli address:
This is not valid either. The nmcli address subcommand doesn’t exist. To manage IP addresses and other interface settings, you would use commands like nmcli device or nmcli connection.

The correct answers are nmcli device and nmcli connection because they are valid subcommands in nmcli that allow users to manage and display device statuses and network connections on a Linux system. nmcli is a powerful tool for system administrators and users who need to work with network configurations from the command line. By mastering these subcommands, one can easily manage wired, wireless, and VPN connections without relying on a graphical interface.

Question No 10:

Which of the following are valid subcommands in nmcli, the command-line interface for NetworkManager? (Choose two.)

A. nmcli ethernet
B. nmcli device
C. nmcli wifi
D. nmcli address
E. nmcli connection

Answer:

B. nmcli device
E. nmcli connection

Explanation:

nmcli is a command-line tool provided by NetworkManager for managing and configuring network connections on Linux-based systems. It is a powerful and flexible tool that can handle network tasks ranging from simple configuration changes to troubleshooting network issues. The nmcli command interacts with the NetworkManager daemon and provides an interface for controlling various aspects of networking, such as device status, connections, and configuration settings.

Let’s examine the valid subcommands in nmcli based on the provided options:

Valid Subcommands:

nmcli device:

Function: The nmcli device subcommand is used to display and manage the status of network devices on a system. It shows details about the network interfaces, such as Ethernet, Wi-Fi, or VPN connections. This subcommand is often used to monitor network devices and check their connection status.

Example Command:
nmcli device status

This command displays the status of all network devices, including whether they are connected, disconnected, or unavailable.
Purpose: Useful for troubleshooting and checking the real-time status of network devices.

nmcli connection:

Function: The nmcli connection subcommand is used to manage network connections. A "connection" in NetworkManager terminology refers to a configuration profile for a network interface. This could be a wired Ethernet connection, a wireless Wi-Fi connection, or even a VPN connection. You can list, modify, delete, and show connections using this subcommand.

Example Command:
nmcli connection show

This command displays all available connections, whether they are active or inactive.
Purpose: Essential for configuring and managing network profiles and connections.

Incorrect Subcommands:

A. nmcli ethernet:

This is not a valid subcommand in nmcli. There is no dedicated subcommand like nmcli ethernet. Ethernet interfaces and settings are managed using the broader nmcli device or nmcli connection subcommands. You would use nmcli device to check the status of Ethernet devices and nmcli connection to configure Ethernet connections.

C. nmcli wifi:

Although you can manage Wi-Fi settings via nmcli, there is no direct nmcli wifi subcommand. Instead, Wi-Fi can be configured with commands such as nmcli device wifi to list available Wi-Fi networks or nmcli connection to manage Wi-Fi profiles.

Example of a valid Wi-Fi command:
nmcli device wifi list

D. nmcli address:

The nmcli address subcommand does not exist. To manage IP addresses and interface configurations, you would use nmcli device or nmcli connection commands. The nmcli tool doesn't have a specific subcommand dedicated to addresses directly.

Why are nmcli device and nmcli connection Correct?

nmcli device allows you to interact with all network devices, giving you information such as whether a device is active and details about its configuration.
nmcli connection gives you the ability to manage and configure network connection profiles, providing a comprehensive way to handle network settings for different interfaces, including wireless, Ethernet, and VPN connections.

In summary, nmcli device and nmcli connection are the correct subcommands for managing devices and connections in NetworkManager. By using these subcommands, users can effectively monitor and configure network devices and connections on Linux systems. Understanding nmcli is an essential skill for system administrators working with network configurations in Linux environments.