202-450 Exam Dumps : LPIC-2 - Exam 202 (part 2 of 2), version 4.5

 TSIG stands for Transaction SIGnature, which is a mechanism for authenticating DNS messages using a shared secret key and a cryptographic hash algorithm. TSIG can be used to secure DNS updates, zone transfers, and queries between DNS servers and clients. To configure a BIND server to use TSIG, the following parameters should be added to the named.conf file:

• A key statement that defines the name, algorithm, and secret of the TSIG key. The name can be any arbitrary string, the algorithm can be one of the supported algorithms such as hmac-md5, hmac-sha1, hmac-sha256, etc., and the secret can be a base64-encoded string that represents the shared secret key. For example:

key “server.example.com” { algorithm hmac-md5; secret “skrKc4DoTzi/takIlPi7JZA==”; };

• A server statement that specifies the IP address or hostname of the remote server that will use the TSIG key, and the name of the key that should be used for communication. For example:

server 192.168.1.10 { keys { “server.example.com”; }; };

• A zone statement that indicates the zone name, type, and file of the zone that will use TSIG, and the name of the key that should be used for updates or transfers. For example:

zone “example.com” { type master; file “example.com.zone”; allow-update { key “server.example.com”; }; allow-transfer { key “server.example.com”; }; };

Option E shows the correct configuration parameters that should be added if the server should use the algorithm hmac-md5 and the key skrKc4DoTzi/takIlPi7JZA==. The other options are incorrect because they either use the wrong syntax, the wrong algorithm, the wrong key name, or the wrong secret.

References:

• LPIC-2 exam 202 objectives, topic 208.2, “Securing a DNS server”
• BIND 9 Administrator Reference Manual, chapter 6, “Access Control Lists and TSIG”
• How to Configure DNS Server with TSIG on CentOS 8

 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 host allow option in the smb.conf file specifies the hosts or networks that are allowed to access the Samba server. The hosts can be specified by name, IP address, or network address with a netmask. The host allow option can also include the special name localhost, which refers to the local machine. The host allow option can be overridden by the host deny option, which specifies the hosts or networks that are denied access to the Samba server. The host deny option has a higher priority than the host allow option.

In this question, the host allow option is set to 192.168.1.100 192.168.2.0/24 localhost, which means that only the host with the IP address 192.168.1.100, the hosts on the network 192.168.2.0/24 (from 192.168.2.1 to 192.168.2.254), and the local machine can access the Samba server. This explains why a wireless laptop with an IP address 192.168.2.93 can access the Samba server, but a workstation on the wired network with an IP address 192.168.1.177 cannot. Almost every machine on the wired network is unable to access the Samba server because they are not included in the host allow option.

To fix this problem, the host allow option should be changed to include the entire wired network, which is assumed to be 192.168.1.0/24 (from 192.168.1.1 to 192.168.1.254). This can be done by using the network address and the netmask, or by using a range of IP addresses. The host allow option should also keep the wireless network and the localhost in the list, so that the existing access is not denied. Therefore, the correct answer is E. host allow = 192.168.1.0/255.255.255.0 192.168.2.0/255.255.255.0 localhost. This will allow any host on either network, or the local machine, to access the Samba server, without denying access to anyone else.