202-450 LPIC-2 - Exam 202 (part 2 of 2), version 4.5 Questions and Answers

To join a file server to an Active Directory domain, the smb.conf file must specify the realm and the workgroup parameters correctly. The realm parameter is the DNS name of the Active Directory domain, in uppercase letters. The workgroup parameter is the NetBIOS name of the domain, which is usually the first part of the DNS name, but can be different. For example, if the DNS name of the domain is intra.example.com, the NetBIOS name could be INTRA or something else. To find out the NetBIOS name of the domain, you can use the command net ads info on a Linux machine that has Samba installed, or the command nltest /dsgetdc:intra.example.com on a Windows machine that is joined to the domain. The other options are either incorrect or irrelevant for this question. 

To create a hidden Samba share, similar to the Windows Administration Share, the share name must end with a dollar sign ().Thiswillpreventthesharefrombeinglistedinthebrowselist,butitcanstillbeaccessedbytypingthefullsharename.OptionAshowsanexampleofahiddenSambasharenamedconfidential, with some additional parameters to configure the share. Option B is incorrect because the share name does not end with a dollar sign. Option C is incorrect because the share name is not enclosed in brackets. Option D is incorrect because the share name contains a space, which is not allowed. Option E is incorrect because the share name is not a valid file name12 References:

• Hiding samba share from browse list for unauthorised users
• Creating a samba share where everyone has write access

The root directive in Nginx defines the file system path from which the content of the server is retrieved. It can be placed in the http, server, or location contexts. The root directive specifies the root directory that will be used to search for a file. To obtain the path of a requested file, Nginx appends the request URI to the path specified by the root directive. For example, if the root directive is set to /var/www/html and the request URI is /index.php, Nginx will look for the file /var/www/html/index.php. References: Serving Static Content | NGINX DocumentationUnderstanding and Implementing FastCGI Proxying in Nginx

 The dig tool is a command-line utility that can query DNS servers and display the results in a human-readable format. The output of dig includes the following sections:

• The header section, which shows the query parameters and response status.
• The question section, which repeats the query name and type.
• The answer section, which shows the resource records that match the query.
• The authority section, which shows the authoritative name servers for the queried domain.
• The additional section, which shows any additional records that may be useful.

The output format of dig is similar to the image provided in the question, which shows the following information:

• The query was for the A record of www.lpi.org.
• The response was received from the DNS server 8.8.8.8.
• The response had an opcode of QUERY, a status of NOERROR, and a flags of QR RD RA.
• The response had 1 question, 1 answer, 0 authority, and 0 additional records.
• The answer record was www.lpi.org. 300 IN A 104.21.23.156, which means that the IP address of www.lpi.org is 104.21.23.156 and has a time-to-live of 300 seconds.

References: dig manual page, dig tutorial

 The required control flag means that the PAM module is essential for the authentication process. If the module fails, the whole authentication fails. However, unlike the requisite control flag, the required control flag does not stop the execution of the remaining modules of the same type. This allows the user to receive feedback from all the modules, such as password expiration warnings or account lockout messages. References:

• Linux Professional Institute LPIC-2 Exam 202-450 Objectives, Topic 211: System Security, Objective 211.2: Configuring PAM, Weight: 5
• PAM Control Flags, System Administration Guide: Security Services, Oracle
• 10.2. About PAM Configuration Files, System-Level Authentication Guide, Red Hat Enterprise Linux 7, Red Hat Customer Portal
• 4. The Linux-PAM configuration file, SCO Group

 The options rw and ro are valid in /etc/exports. They specify whether the exported file system is mounted with read-write or read-only permissions by the clients. The option rw allows the clients to modify the files on the server, while the option ro prevents any changes by the clients. These options can be applied to all or specific hosts in the /etc/exports file123 References:

• LPIC-2 Overview
• LPIC-2 202-450
• 10 practical examples to export NFS shares in Linux | GoLinuxCloud

The LDIF file format does not accept any type of file encoding. It requires the file to be encoded in UTF-8, which is a Unicode encoding that supports all characters and languages. If the file contains non-UTF-8 characters, it may cause errors or data loss when importing or exporting LDIF data. Therefore, it is important to ensure that the LDIF file is encoded in UTF-8 before using it with LDAP tools or servers. References:

• LDIF File (What It Is and How to Open One) - Lifewire
• RFC 2849 - The LDAP Data Interchange Format (LDIF) - Technical Specification

 The line A is valid in a configuration file in /etc/pam.d/ because it follows the correct syntax and semantics of a PAM configuration file. The syntax of a PAM configuration file is:

module_interface control_flag module_name module_arguments

The module_interface specifies the type of authentication action that the module can perform. There are four types of module interface: auth, account, password, and session. The control_flag specifies how important the success or failure of the module is to the overall authentication process. There are four types of control flag: required, requisite, sufficient, and optional. The module_name specifies the name of the library that contains the module. The module_arguments are optional parameters that can modify the behavior of the module.

The line A has the following components:

• module_interface: auth, which means the module is used for user authentication.
• control_flag: required, which means the module must succeed for authentication to continue. If the module fails, the failure is recorded and the rest of the modules are executed.
• module_name: pam_unix.so, which means the module is the standard Unix authentication module that verifies the user’s password against the /etc/passwd and /etc/shadow files.
• module_arguments: try_first_pass nullok, which means the module tries to use the password that was previously entered by the user (if any), and allows users with empty passwords to log in.

The line B is invalid because it has the wrong order of the fields. The control_flag should come before the module_name, not after. The line C is invalid because it uses parentheses and colons instead of spaces to separate the fields. The line D is invalid because it has the wrong syntax for the control_flag. The control_flag should be a single word, not a word in parentheses.

The doveadm who sub-command shows information about the currently connected users and their sessions. The output includes the following columns:

• user: The username of the connected user.
• ip: The IP address of the client.
• port: The port number of the client.
• service: The name of the Dovecot service, such as imap, pop3, lmtp, etc.
• protocol: The protocol version used by the client, such as IMAP4rev1, POP3, etc.
• pid: The process ID of the Dovecot process that handles the connection.
• type: The type of the connection, such as tcp, ssl, etc.
• state: The state of the connection, such as running, idle, etc.
• since: The time when the connection was established.

References:

• doveadm-who - Dovecot Wiki
• LPIC-2 exam 202 objectives, topic 211.3, “Managing Mailbox Access”

The newaliases command is a Postfix command that can be used to rebuild all of the alias database files with a single invocation and without the need for any command line arguments. The newaliases command is equivalent to running the postalias command on each file specified by the alias_database parameter in the Postfix main.cf configuration file. The newaliases command reads the text files that contain the alias definitions and creates the indexed files in dbm or db format that are used for fast lookup by the mail system. The newaliases command should be executed whenever the alias database is changed, in order to update the indexed files. For example:

newaliases

The other commands are not equivalent to the newaliases command. The makealiases command is not a valid Postfix command. The postalias command can be used to rebuild a single alias database file, but it requires the file name as an argument. The postmapbuild command is not a valid Postfix command.

References:

• LPIC-2 Exam 202 Objectives, Objective 205.3: Managing a postfix server
• Postfix Basic Configuration, Postfix Documentation
• Postfix manual - aliases(5), Postfix Documentation
• Postfix manual - newaliases(1), Postfix Documentation
• Postfix manual - postalias(1), Postfix Documentation

The PAM module that sets and unsets environment variables is pam_env. This module allows the (un)setting of environment variables based on the rules specified in the configuration file /etc/security/pam_env.conf or an alternative file. The module can also read a file with simple KEY=VAL pairs on separate lines (/etc/environment by default) or a user-specific file ($HOME/.pam_environment by default). The pam_env module supports the use of previously set environment variables as well as PAM_ITEMs such as PAM_RHOST. The pam_env module should be the last one on the stack, as setting PAM environment variables can have side effects on other modules. The pam_env module provides the auth and session module types. References:

• pam_env - PAM module to set/unset environment variables
• pam_env(8) - Linux manual page

The AuthType directive is used to specify the method of authentication for a directory or a location on the Apache HTTPD server. The directive has four possible values: None, Basic, Digest, and Form. Each value corresponds to a different module that implements the authentication mechanism.

• None: This value means that no authentication is required. This is the default value and it can be used to override any inherited authentication settings.
• Basic: This value means that the basic authentication method is used. This method is implemented by the mod_auth_basic module. It requires the user to enter a username and a password, which are sent to the server in plain text. Therefore, this method is not very secure and should be used with encryption, such as SSL or TLS.
• Digest: This value means that the digest authentication method is used. This method is implemented by the mod_auth_digest module. It requires the user to enter a username and a password, which are hashed by the client and the server using a nonce (a random number) and a realm (a name for the protected area). Therefore, this method is more secure than the basic method, as it prevents replay attacks and password sniffing.
• Form: This value means that the form authentication method is used. This method is implemented by the mod_auth_form module. It requires the user to fill out a web form with their credentials, which are sent to the server using the POST method. Therefore, this method is more flexible and user-friendly than the other methods, as it allows the use of custom forms and cookies.

References:

• AuthType Directive
• Authentication and Authorization - Apache HTTP Server Version 2.4
• How to Create and Use .htpasswd

The command that displays NFS kernel statistics is nfsstat. This command can be used to show information about the number and type of NFS and RPC calls made by the NFS client or server. It can also be used to reset the statistics to zero, or to display information about mounted NFS file systems. The nfsstat command is part of the nfs-utils package and can be installed on most Linux distributions. For more information about the nfsstat command, you can refer to the following resources:

• 1: A Microsoft Learn article that explains the syntax and usage of the nfsstat command on Windows Server.
• 2: A Bing search result page that shows various links and snippets related to the nfsstat command.
• 3: A Red Hat article that demonstrates how to use the nfsstat and nfsiostat commands to troubleshoot NFS performance issues on Linux.

 The Linux user that is used by vsftpd to perform file system operations for anonymous FTP users is the one specified in the configuration option ftp_username. This option defines the local user that vsftpd will run as when handling anonymous FTP requests. By default, this option is set to ‘ftp’, which is a predefined user account that has limited privileges and access to the FTP server. The other options are incorrect for the following reasons:

• A. The Linux user which runs the vsftpd process. This is false because vsftpd does not use the same user that runs the daemon to handle anonymous FTP requests. Instead, it switches to the user specified by ftp_username, which is usually a different and less privileged user than the one that starts the vsftpd process.
• B. The Linux user that owns the root FTP directory served by vsftpd. This is false because vsftpd does not use the owner of the root FTP directory to perform file system operations for anonymous FTP users. The owner of the root FTP directory may or may not be the same as the user specified by ftp_username, but it does not affect the behavior of vsftpd for anonymous FTP requests.
• C. The Linux user with the same user name that was used to anonymously log into the FTP server. This is false because vsftpd does not use the user name that was used to anonymously log into the FTP server to perform file system operations. The user name that is used for anonymous FTP login is usually ‘anonymous’ or ‘ftp’, but it does not correspond to any actual Linux user account on the system. Instead, vsftpd maps these user names to the user specified by ftp_username, which is the one that actually performs the file system operations.
• D. The Linux user root, but vsftpd grants access to anonymous users only to globally read-/writeable files. This is false because vsftpd does not use the root user to perform file system operations for anonymous FTP users. The root user is the most powerful and privileged user on the system, and using it for anonymous FTP requests would pose a serious security risk. Instead, vsftpd uses the user specified by ftp_username, which is usually a low-privileged user that has limited access to the FTP server. The option anon_world_readable_only controls whether vsftpd only allows anonymous users to access files that have global read permissions, regardless of the permissions of the user specified by ftp_username.

References: LPIC-2 202 exam objectives, LPIC-2 202-450 Exam Prep: Network Configuration, Reference Manual For OpenVPN 2.4, linux - What is the anonymous user in vsftp? - Super User

How To Set Up vsftpd for Anonymous Downloads on Ubuntu 16.04

 The sender_canonical_maps parameter on a Postfix server specifies an optional address mapping that applies when mail is delivered (sent) from the server. This mapping can be used to rewrite the sender address of outgoing messages to a different format or domain. For example, the following sender_canonical_maps entry will rewrite the sender address from user@localdomain to user@example.com:

user@localdomain user@example.com

The sender_canonical_maps parameter only affects the sender address and not the recipient address. The recipient address can be modified by other parameters such as recipient_canonical_maps or virtual_alias_maps.

References: You can learn more about sender_canonical_maps and other Postfix address rewriting parameters from the following sources:

• Postfix Address Rewriting
• Postfix Configuration Parameters
• Postfix Generic Mapping for Outgoing SMTP Mail

The dig command in the image shows that the reverse DNS lookup for the IP address 192.168.0.1 failed to return the expected hostname linuserv.example.net. Instead, it returned linuserv.example.net.example.net, which indicates that the PTR record in the reverse lookup zone file is missing a dot (.) at the end of the hostname. Without the dot, the hostname is treated as relative to the zone name, which is example.net. Therefore, the correct syntax for the PTR record in the reverse lookup zone file should be:

1.168.192.in-addr.arpa. IN PTR linuserv.example.net.

The dot at the end of the hostname makes it absolute, meaning it does not append the zone name to it. This way, the reverse DNS lookup will return the correct hostname for the IP address123 References:

• Reverse DNS Lookup - WhatIsMyIP.com®
• DNS PTR Records - DNSimple Help
• How to Configure Reverse DNS for BIND in WHM - cPanel Knowledge Base - cPanel Documentation

What is a DNS PTR Record? PTR Record Syntax & Examples - PowerDMARC

The LDIF excerpt shows the distinguished name (dn) of Robert Smith as “cn=Robert Smith, ou=people, dc=example, dc=com”. The organizational unit (ou) attribute is used to represent an organizational unit in which an entry resides. In this case, Robert Smith is part of the “people” organizational unit.

References:

• [OpenLDAP Software 2.6 Administrator’s Guide: The LDIF File Format]: The official documentation of OpenLDAP on the LDIF file format, which explains the syntax and structure of LDIF entries and attributes.
• [LDAP Data Interchange Format (LDIF) - Version 1]: The RFC 2849 document that defines the LDAP Data Interchange Format (LDIF), which is a common format for exchanging LDAP data.

 The NFSv4 pseudo file system is a virtual file system that provides a single root directory for all the exports on the NFS server. It allows the clients to see all the exports as a single file system, regardless of their physical locations on the server. The pseudo file system usually contains bind mounts of the directory trees to be exported, which are created using the mount --bind command. Bind mounts create a second mount point for an existing directory, without changing its attributes or permissions. This way, the pseudo file system can include directories from different file systems or partitions on the server123 References:

• NFSv4Howto - Community Help Wiki
• NFSv4: Enhancements and Best Practices Guide - NetApp
• File-System Namespace in NFS Version 4 - Oracle

The option that would tell OpenVPN to use a dynamic source port when making a connection to a peer is nobind. This option instructs OpenVPN to not bind to a specific local port number, but instead use an ephemeral port number chosen by the operating system. This allows multiple OpenVPN instances to connect to the same remote server or peer without port conflicts. The other options are either invalid or have different meanings:

• src-port: This is not a valid OpenVPN option and will cause an error.
• remote: This option specifies the host name or IP address and port number of the remote server or peer to connect to. It does not affect the source port of the client.
• source-port: This is not a valid OpenVPN option and will cause an error.
• dynamic-bind: This is not a valid OpenVPN option and will cause an error.

References: LPIC-2 202 exam objectives, LPIC-2 202-450 Exam Prep: Network Configuration, Reference Manual For OpenVPN 2.4

 The FTP names that are recognized as anonymous users in vsftpd when the option anonymous_enable is set to yes in the configuration file are anonymous and ftp. These are the default names that vsftpd accepts as valid anonymous users, and they can be used interchangeably. The anonymous user does not need to enter a password, but can optionally enter an email address as a password. The anonymous user has limited permissions and can only access the directory specified by the anon_root directive, which is usually /var/ftp or /srv/ftp. The anonymous user can download files from the server, but cannot upload or modify files, unless the anon_upload_enable and anon_mkdir_write_enable directives are also set to yes.

The other options are not recognized as anonymous users in vsftpd. Option C is incorrect, because vsftpd will reject any username that does not belong to an existing user or an anonymous user. Option D is incorrect, because nobody is a system user that has no permissions and is not related to FTP. Option E is incorrect, because guest is not a valid FTP name, unless the guest_enable directive is set to yes, which will make all non-anonymous users log in as the guest_username, which is usually ftp.

References:

• vsftpd.conf - config file for vsftpd
• How To Set Up vsftpd for Anonymous Downloads on Ubuntu 16.04
• How to Configure vsftpd FTP Server on CentOS 8

 A certificate signing request (CSR) is a message sent from an applicant to a certificate authority (CA) in order to apply for a digital identity certificate. The CSR contains information about the applicant’s identity, such as domain name, organization, location, etc., as well as the applicant’s public key. The CSR is digitally signed by the applicant using their private key, which proves that they own the corresponding public key. The CA will verify the CSR and issue a certificate if the applicant meets the requirements. The certificate will contain the applicant’s public key and identity information, as well as the CA’s digital signature, which validates the certificate. References: LPIC-2 Exam 202 Objectives, What is a Certificate Signing Request (CSR)? Do I need one?

 The option within the ISC DHCPD configuration file that defines the IPv4 DNS server address(es) to be sent to the DHCP clients is domain-name-servers. This option takes one or more IPv4 addresses as arguments and specifies the DNS servers that the client should use for name resolution. The domain-name-servers option is part of the standard DHCP options defined in RFC 2132 and is supported by the ISC DHCP server. The domain-name-servers option can be specified globally, per subnet, per shared network, per group, or per host in the dhcpd.conf file. For example, the following line in the dhcpd.conf file will assign the DNS servers 192.168.1.1 and 192.168.1.2 to all DHCP clients:

option domain-name-servers 192.168.1.1, 192.168.1.2;

References:

• ISC DHCP 4.4 Manual Pages - dhcp-options
• [RFC 2132 - DHCP Options and BOOTP Vendor Extensions]
• isc-dhcp-server - Community Help Wiki - Official Ubuntu Documentation

The command that creates a SSH key pair is ssh-keygen. This command generates a public and a private key file that can be used for SSH authentication. The command can take various options to specify the algorithm, the file name, the passphrase, and other parameters for the key pair. For more information, see the web search results below or the man page of ssh-keygen.

How to Use ssh-keygen to Generate a New SSH Key?

 In a BIND zone file, the @ character indicates the name of the zone as defined in the zone statement in named.conf. This is also known as the current origin of the zone file. The @ character is a shortcut that allows the zone file to refer to the zone name without typing it fully. For example, if the zone name is example.com, then the @ character can be used instead of example.com. in the zone file. This can save space and avoid typos123 References:

• LPIC-2 Overview
• LPIC-2 202-450
• What’s the meaning of ‘@’ in a DNS zone file? - Server Fault

Sieve filters are usually applied to an email when the email is delivered to a mailbox by a mail delivery agent (MDA) or a local delivery agent (LDA). Sieve filters are scripts that can perform various actions on incoming emails, such as sorting them into folders, assigning labels, forwarding, rejecting, or discarding them. Sieve filters are executed on the server side, and they are independent of the mail user agent (MUA) or the mail access protocol. This means that the email filtering is consistent across different email clients and devices. Sieve filters are not applied when the email is relayed by an SMTP server, received by an SMTP smarthost, sent to the first server by an MUA, or retrieved by an MUA. These are different stages of the email delivery process, but they do not involve the final delivery of the email to a mailbox.

References:

• LPIC-2 Exam 202 Objectives, Objective 205.4: Managing a dovecot server
• Sieve filter (advanced custom filters) | Proton
• start - Sieve.Info
• What is Sieve Filtering? - Knowledge Base - Pair Networks

 Reverse DNS queries are used to find the domain name associated with an IP address. To perform reverse DNS queries, DNS servers use a special type of record called PTR (pointer) record. A PTR record maps an IP address to a hostname in the reverse lookup zone. For example, a PTR record for the IP address 185.230.63.186 would point to the hostname unalocated.63.wixsite.com. Reverse DNS queries are useful for validating email servers, troubleshooting network problems, and identifying malicious hosts. References:

• 2 Ways to Perform Reverse DNS lookups in Linux - howtouselinux
• Linux managing DNS servers (LPIC-2) · GitHub
• LPI Linux Certification/LPIC2 Exam 202/DNS - Wikibooks

 PAM modules are organized and stored as shared object files within the /lib/ directory hierarchy. A shared object file is a file that contains executable code and data that can be loaded into memory and used by one or more programs. This allows PAM modules to be dynamically loaded and unloaded by the PAM library as needed, without requiring recompilation or relinking of the programs that use them. The /lib/ directory hierarchy contains subdirectories for different architectures and operating systems, such as /lib/x86_64-linux-gnu/ or /lib64/. The PAM modules are usually located in a subdirectory named security, such as /lib/x86_64-linux-gnu/security/ or /lib64/security/. The PAM modules have names that start with pam_ and end with .so, such as pam_unix.so or pam_cracklib.so12.

References:

• PAM Modules: A section from the Linux-PAM System Administrators’ Guide that explains what PAM modules are, how they are named, and where they are located.
• An introduction to Pluggable Authentication Modules (PAM) in Linux: An article from Red Hat that introduces the concept and usage of PAM in Linux, which includes a description of PAM modules and their location.

The rndc sub command that can be used in conjunction with the name of a zone in order to make BIND reread the content of the specific zone file without reloading other zones as well is reload. The reload sub command instructs the BIND server to reload the specified zone or all zones if no zone is specified. The reload sub command is useful for applying changes made to the zone files without restarting the BIND service or affecting other zones. The syntax of the reload sub command is as follows:

rndc reload [zone [class [view]]]

For example, to reload the zone example.com in the IN class and the default view, use the following command:

rndc reload example.com IN

References:

• rndc - man pages section 8: System Administration Commands, sub command “reload”
• 17.2.3. Using the rndc Utility - Red Hat Customer Portal, section “Reloading the Configuration and Zones”

The option in named.conf that specifies which hosts are permitted to ask for domain name information from the server is allow-query. The allow-query option is used to define an access control list (ACL) that matches the source IP address of the DNS query. The ACL can be a list of IP addresses, networks, keywords, or predefined ACL names. The default value of allow-query is any, which means that any host can query the server. However, this can pose a security risk, as the server may be exposed to unwanted or malicious queries. Therefore, it is recommended to restrict the allow-query option to only the hosts that need to access the server, such as the local network or trusted clients. For example, the following option allows only the hosts in the 192.168.1.0/24 network and the localhost to query the server:

allow-query { 192.168.1.0/24; localhost; };

The other options are not valid in named.conf. allowed-hosts, accept-query, permit-query, and query-group are not recognized keywords by BIND.

References:

• LPIC-2 exam 202 objectives, topic 208.1, “Implementing a web server”
• BIND 9 Administrator Reference Manual, chapter 6, “Access Control Lists and TSIG”
• How to Configure DNS Server with TSIG on CentOS 8

mount-tnfsv4 server://mnt

of an NFC-Client, it is observed that /mnt contains the content of the server’s /usr directory instead of the content of the NFSv4 foot folder.

Which option in /etc/exports has to be changed or removed in order to make the NFSv4 root folder appear when mounting the highest level of the server? (Specify ONLY the option name without any values or parameters.)

Answer:  fsid

The fsid option in /etc/exports is used to specify a unique identifier for each exported filesystem. For NFSv4, there is a distinguished filesystem which is the root of all exported filesystems, and it is specified with fsid=root or fsid=0, both of which mean the same thing. If this option is used for the /exports directory, then it will be the root of the NFSv4 hierarchy, and any subdirectories under it will be mounted relative to it. This means that when mounting the highest level of the server, the client will see the content of /exports instead of the NFSv4 root folder. To avoid this, the fsid option should be removed or changed to a different value for the /exports directory, so that it is not the NFSv4 root. The other options in /etc/exports are not relevant for this question.

The word missing from the excerpt of a named.conf file is “acl”. This is because the excerpt is defining an access control list (ACL) for the DNS server. The ACL is used to restrict access to the DNS server and is defined in the named.conf file. The syntax for defining an ACL is:

acl name { address_match_list; };

where name is the name of the ACL, and address_match_list is a list of IP addresses, networks, or keywords that match the clients that are allowed or denied access.References:

• LPIC-2 Overview
• LPIC-2 202-450
• BIND 9 Administrator Reference Manual

Fail2ban is a tool that monitors the system logs for failed login attempts and blocks the offending IP addresses using netfilter rules. Netfilter is a framework that provides packet filtering, network address translation, and other functions for the Linux kernel. Fail2ban uses the iptables command to manipulate the netfilter rules and create chains of rules that match the source IP address of the attacker and drop or reject the packets from that IP address. Fail2ban can also use other firewall tools, such as firewalld or ufw, to create the netfilter rules. Fail2ban can block the IP addresses for a specified amount of time, or permanently, depending on the configuration. Fail2ban can protect various services, such as SSH, HTTP, FTP, etc., by creating different jails for each service. A jail is a set of parameters that define how to monitor a log file, how to detect a failed login attempt, how to ban an IP address, and how long to keep the ban.

Fail2ban does not block offending SSH clients by any of the other options. It does not act as a proxy in front of SSHD, nor does it modify the SSHD configuration. It does not create null routes that drop any answer packets sent to the client, nor does it modify the TCP Wrapper configuration for SSHD.

References:

• How To Protect SSH with Fail2Ban on Ubuntu 20.04
• How To Prevent SSH Brute Force Attacks Using Fail2ban In Linux
• Fail2ban - Wikipedia
• Fail2ban Manual