Free Practice Questions for LPI 102-500 Exam

The statement hosts: files dns is valid in the file /etc/nsswitch.conf. It means that the system will use the local /etc/hosts file and the Domain Name System (DNS) to resolve host names to IP addresses. The order of the sources on the line determines the order in which they will be queried. In this case, the system will first check the /etc/hosts file for a matching host name, and if not found, it will query the DNS servers configured in /etc/resolv.conf. The other statements in the question are not valid in the /etc/nsswitch.conf file. The statement multi on is not a valid keyword or source for any database. The statement 192.168.168.4 dns-server is not a valid syntax for specifying a source or an action. The statement include /etc/nsswitch.d/ is not a valid way to include another file or directory in the /etc/nsswitch.conf file. References:

[LPI Linux Administrator - Exam 102 Objectives - Topic 109: Networking Fundamentals]

nsswitch.conf(5) - Linux manual page

What is the /etc/nsswitch.conf file in Linux – TecAdmin

 Network interfaces may become active or inactive, the routing table may change, and IP addresses may change. Comprehensive Explanation: The ifconfig command is a network management tool that is used to configure and view the status of the network interfaces in Linux operating systems1. With ifconfig, you can assign IP addresses, enable or disable interfaces, manage ARP cache, routes, and more1. Some of the possible consequences of using the ifconfig command are:

Network interfaces may become active or inactive. The ifconfig command can take an interface name as an argument and display the configuration information for that interface. For example, to view the configuration of the eth0 interface, one can run:

ifconfig eth0

The output shows whether the interface is UP or DOWN, meaning active or inactive. The ifconfig command can also activate or deactivate an interface by using the up or down options. For example, to deactivate the eth0 interface, one can run:

sudo ifconfig eth0 down

To activate the eth0 interface, one can run:

sudo ifconfig eth0 up

The routing table may change. The ifconfig command can assign IP addresses, netmask, and broadcast address to a network interface. For example, to assign an IP address of 192.168.1.10, a netmask of 255.255.255.0, and a broadcast address of 192.168.1.255 to the eth0 interface, one can run:

sudo ifconfig eth0 192.168.1.10 netmask 255.255.255.0 broadcast 192.168.1.255

These parameters affect the routing table, which is a list of rules that determine where the packets are sent. The routing table can be viewed by using the route command. For example, to view the routing table, one can run:

route -n

The output shows the destination, gateway, netmask, flags, metric, reference, use, and interface for each route. The ifconfig command can also delete an IP address from an interface, which may remove the corresponding route from the routing table. For example, to delete the IP address of 192.168.1.10 from the eth0 interface, one can run:

sudo ifconfig eth0 0

IP addresses may change. The ifconfig command can assign or delete IP addresses to a network interface, as explained above. The IP address is a unique identifier that allows the network interface to communicate with other devices on the network. The IP address can be viewed by using the ifconfig command without any options or with the interface name only. For example, to view the IP address of the eth0 interface, one can run:

ifconfig eth0

The output shows the inet addr, which is the IP address of the interface. The ifconfig command can also create an alias for the network interface, which is a virtual interface that shares the same physical interface but has a different IP address. For example, to create an alias for the eth0 interface with an IP address of 192.168.1.11, one can run:

sudo ifconfig eth0:0 192.168.1.11

The alias can be viewed by using the ifconfig command with the alias name. For example, to view the configuration of the eth0:0 alias, one can run:

ifconfig eth0:0

The output shows the inet addr, which is the IP address of the alias.

The other options are not correct because:

New name servers may be added to the resolver configuration. The ifconfig command does not affect the resolver configuration, which is a file that contains the names and addresses of the name servers that resolve domain names to IP addresses. The resolver configuration is stored in the /etc/resolv.conf file and can be viewed or edited by using a text editor. For example, to view the resolver configuration, one can run:

cat /etc/resolv.conf

The output shows the nameserver entries, which are the IP addresses of the name servers. The ifconfig command does not add or remove name servers from this file.

The system’s host name may change. The ifconfig command does not affect the host name, which is a name that identifies the system on the network. The host name is stored in the /etc/hostname file and can be viewed or edited by using a text editor. For example, to view the host name, one can run:

cat /etc/hostname

The output shows the host name of the system. The ifconfig command does not change the host name of the system. References:

https://linuxize.com/post/ifconfig-command/

https://www.ibm.com/docs/en/aix/7.2?topic=i-ifconfig-command

 The command to delete the default gateway from the system IP routing table is either route del default or ip route del default. Both commands will remove the default route that matches the specified parameters. The route command is the older and more widely supported tool, while the ip command is the newer and more powerful tool that can manipulate various aspects of the network configuration. The other options are either invalid or do not affect the default gateway. References:

1: How to Remove Default Gateways via ip | Baeldung on Linux

2: How to remove all default gateways - Unix & Linux Stack Exchange

4: How to Add or Change the Default Gateway in Linux: 9 Steps - wikiHow

To find the number of IP-addresses that can be used for unique hosts inside an IPv4 subnet, we need to calculate the number of bits that are used for the host part of the IP address. The host part is the part that is not used for the network prefix, which is indicated by the slash notation (/) followed by a number. The number after the slash represents the number of bits that are used for the network prefix, out of the total 32 bits of an IPv4 address. The remaining bits are used for the host part. For example, in the subnet 192.168.2.128/28, the number 28 means that the first 28 bits are used for the network prefix, and the last 4 bits are used for the host part.

The number of IP-addresses that can be used for unique hosts is equal to 2^n - 2, where n is the number of bits in the host part. The -2 is because the first and the last IP addresses in a subnet are reserved for the network address and the broadcast address, respectively, and cannot be assigned to hosts. Therefore, in the subnet 192.168.2.128/28, the number of IP-addresses that can be used for unique hosts is 2^4 - 2, which is 14.

References:

IPv4 - Subnetting - Online Tutorials Library

IP Subnet Calculator

 The netstat command, meaning network statistics, is a command-line utility in the Linux system to display network configuration and activity, including network connections, routing tables, interface statistics, masquerade connections, and multicast memberships1. The netstat command can display different types of network data depending on the command line option selected. Some of the common options are:

-a: This option displays active TCP connections, TCP connections with the listening state, as well as UDP ports that are being listened to.

-r: This option displays the routing table information, which is a list of rules that determine where the packets are sent.

-i: This option displays the network interface information, such as the name, MTU, RX-OK, TX-OK, etc.

-s: This option displays the network statistics by protocol, such as TCP, UDP, ICMP, IP, etc.

For example, to display the open network connections, one can run:

netstat -a

To display the routing table, one can run:

netstat -r

To display the network interface statistics, one can run:

netstat -i

To display the network statistics by protocol, one can run:

netstat -s

For more details and examples, please refer to the web search results1 or the question answering results2. References:

https://netref.soe.ucsc.edu/node/7

https://bing.com/search?q=command+to+display+network+connections%2c+routing+tables%2c+and+interface+statistics

The route command displays the kernel’s routing table, which contains information about how packets are routed to different destinations. By default, route tries to resolve the IP addresses of the routers and destinations to their hostnames using DNS. If DNS is not working properly, this can cause a delay in displaying the routing table as route waits for the DNS queries to time out. To avoid this, route can be used with the -n option, which prevents DNS lookups and displays only numeric addresses. References:

LPI 102-500 Exam Objectives, Topic 109: Network Fundamentals, 109.3 Basic network troubleshooting

LPI 102-500 Study Guide, Chapter 9: Network Troubleshooting, Section 9.2: Troubleshooting Routing Problems

Broadcast addresses are used to send a message to all devices on a network segment. IPv4 supports broadcast addresses, but IPv6 does not. Instead, IPv6 uses multicast addresses, which are used to send a message to a group of devices that have joined a multicast group. Multicast addresses are more efficient and flexible than broadcast addresses, as they allow the sender to specify the recipients more precisely and avoid unnecessary network traffic. IPv6 also supports anycast addresses, which are used to send a message to the nearest device that provides a specific service. Anycast addresses are useful for load balancing and redundancy. References:

[LPI Linux Administrator - Exam 102 Objectives - Topic 109: Networking Fundamentals]

IPv6 - Features - Online Tutorials Library

IPv6 - Wikipedia

 The nsswitch.conf file is a configuration file that determines the sources and the order of the sources that are queried for various system databases, such as user information, group information, host names, network services, and more. The C library uses this file to look up various system information when a program or a command requests it. For example, when a user logs in, the C library will use the nsswitch.conf file to determine where to find the user’s password, whether it is in the local /etc/passwd file, or in a remote LDAP server, or both. The nsswitch.conf file allows the system administrator to configure the system databases in a flexible and modular way. References:

[LPI Linux Essentials - Topic 106: The Linux Operating System]

[LPI Linux Administrator - Exam 102 Objectives - Topic 110: Security]

[Linux man page for nsswitch.conf]

The commands that can be used to display the local routing table are netstat and route. Both commands can show the kernel routing tables, which contain information about the network destinations and the gateways to reach them. The netstat command can be used with the -r option to display the routing table, and the -n option to show numeric addresses only. The route command can also be used with the -n option to display the routing table without resolving names. However, both netstat and route are considered obsolete and have been replaced by the ip route command, which is the current recommended way of printing the routing table in Linux12. References:

1: Understanding Routing Table - nixCraft

2: How To Display Routing Table In Linux - RootUsers

3: linux networking - What is the local routing table used for? - Server Fault

The lowest numbered unprivileged TCP port is 1024. A port number is a 16-bit unsigned integer, thus ranging from 0 to 65535. The port numbers in the range from 0 to 1023 are the well-known ports or system ports. They are used by system processes that provide widely used types of network services. On Unix-like operating systems, a process must execute with superuser privileges to be able to bind a network socket to an IP address using one of the well-known ports. Therefore, the lowest numbered port that can be used by a normal user without root access is 1024, which is the first unprivileged port123 References:

1: How to bind to port number less than 1024 with non root access?

2: lowest numbered unprivileged TCP port - Bing

3: List of TCP and UDP port numbers - Wikipedia

4: Privileged Ports - World Wide Web Consortium (W3C)

5: What is the lowest TCP port number? – TeachersCollegesj