102-500 Exam Dumps - LPIC-1 Exam 102, Part 2 of 2, version 5.0

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

 The keywords dns and files can be used in the /etc/nsswitch.conf file to specify a source for host name lookups. The keyword dns means that the system will use the Domain Name System (DNS) to resolve host names to IP addresses. The keyword files means that the system will use the local /etc/hosts file to resolve host names to IP addresses. The order of the keywords on the line determines the order in which the sources will be queried. For example, the following line in /etc/nsswitch.conf:

hosts: files dns

means that 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 keywords in the question are not valid for the hosts database. The keyword resolv is used for the services database, which contains network service names and port numbers. The keyword remote is not a standard keyword, but it may be used by some applications to implement their own name service providers. The keyword hosts is the name of the database itself, not a source for it. 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

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

A valid IPv6 address is represented as a set of 16-bit hexadecimals separated by colons. The address is divided into eight groups, and each 16-bit group is represented by four hexadecimal numbers. A valid IPv6 address is in the form “x1:x2:x3:x4:x5:x6:x7:x8” where each xi is a hexadecimal string which may contain digits, lower-case English letter (‘a’ to ‘f’) and upper-case English letters (‘A’ to ‘F’). Leading zeros are allowed in xi. The longest sequence of consecutive all-zero fields is replaced with two colons (::).1

Option A is the only one that follows these rules. Option B has two consecutive colons twice, which is not allowed. Option C has an invalid hexadecimal character ‘g’. Option D uses percentage signs instead of colons, which is not a valid separator. Option E uses dots instead of colons, and has two consecutive dots, which are both invalid.

References: 1: IPv4 and IPv6 address formats - IBM

The file /etc/resolv.conf is the configuration file for the DNS resolver, which translates domain names to IP addresses by querying the DNS servers. The file supports several keywords that provide various types of resolver information. Two of the keywords that can be used in /etc/resolv.conf are:

nameserver: This keyword specifies the IP address of the DNS server that the resolver can query against. Up to three nameservers can be configured, and the resolver will try them in order until one responds or all fail.

search: This keyword specifies a list of search domains that the resolver will append to the domain name when performing a query. For example, if the search list is example.com example.net, and the resolver queries for host, it will try host.example.com and host.example.net in order. The search list can have up to six domains, with a maximum of 256 characters in total.

The other keywords in the question are not valid for /etc/resolv.conf. The file does not support any keywords for substitution, lookup, or method. However, there are other keywords that can be used, such as:

domain: This keyword specifies the local domain name of the system. It is mutually exclusive with the search keyword, and only one instance of either can be used.

options: This keyword specifies various options that modify the behavior of the resolver. For example, the option rotate can be used to rotate the nameservers in a round-robin fashion, instead of trying them in order. Multiple options can be specified, separated by spaces.

References:

3: The /etc/resolv.conf File | Baeldung on Linux

1: /etc/resolv.conf - QNX

4: Chapter 33. Manually configuring the /etc/resolv.conf file

 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 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 command ifconfig can be used to set a network interface active or inactive by using the up or down options. For example, the following command will activate the eth0 interface:

sudo ifconfig eth0 up

The command ifconfig can also be used to change the netmask used on a network interface by specifying the netmask option followed by the desired netmask value. For example, the following command will change the netmask of the eth0 interface to 255.255.255.0:

sudo ifconfig eth0 netmask 255.255.255.0

The other options in the question are not possible with the ifconfig command. The command ifconfig cannot specify the kernel module to be used with a network interface. This is done by the modprobe command or the /etc/modules file. The command ifconfig cannot allow regular users to change the network configuration of a network interface. This is controlled by the sudoers file or the polkit framework. The command ifconfig cannot specify which network services are available on a network interface. This is done by the firewall rules or the /etc/services file. References:

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

Linux ifconfig Command | Linuxize

15 Useful “ifconfig” Commands to Configure Network in Linux - Tecmint

ifconfig command in Linux with Examples - GeeksforGeeks