LPI 202-450 Dumps Questions Answers

 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.

 DHCPv6 supports three types of IPv6 address assignments:

• Individual address assignment (IA_NA): This is the stateful mode of DHCPv6, where the DHCPv6 server assigns a normal IPv6 address to a client that can be renewed or released. The address is chosen from a pool of prefixes configured on the server and is unique and non-duplicate. The client can request one or more addresses using the IA_NA option in the DHCPv6 messages1
• Temporary address assignment (IA_TA): This is similar to the IA_NA mode, but the addresses assigned are temporary and cannot be renewed or released. The temporary addresses are used for privacy reasons and are generated by the client using a random interface identifier. The client can request one or more temporary addresses using the IA_TA option in the DHCPv6 messages2
• Prefix delegation (IA_PD): This is the mode where the DHCPv6 server delegates a whole IPv6 prefix to a client, such as a router or a host, that can use it for further subnetting or routing. The client can request one or more prefixes using the IA_PD option in the DHCPv6 messages. The delegated prefixes are also chosen from a pool of prefixes configured on the server3

References: 1: IP Addressing: DHCP Configuration Guide - IPv6 Access Services: DHCPv6 Individual Address Assignment 2: RFC 4941 - Privacy Extensions for Stateless Address Autoconfiguration in IPv6 3: IP Addressing: DHCP Configuration Guide - IPv6 Access Services: DHCPv6 Prefix Delegation

An open relay is a mail server that allows anyone to send e-mail through it without authentication or authorization. This can expose the mail server to spam, abuse, and blacklisting. To prevent the mail server from being used as an open relay, while maintaining the possibility to receive company mails, the following actions would help:

• Restrict Postfix to only accept e-mail for domains hosted on this server. This can be done by setting the mydestination parameter in the /etc/postfix/main.cf file to include the company domains, and the smtpd_recipient_restrictions parameter to reject_unauth_destination. This will ensure that Postfix will only accept mail for the domains that it is responsible for, and reject mail for other domains unless the sender is authenticated or authorized. For example:

mydestination = example.com, example.net, localhost smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination

• Restrict Postfix to only relay outbound SMTP from the internal network. This can be done by setting the mynetworks parameter in the /etc/postfix/main.cf file to include the IP addresses or networks of the internal hosts that are allowed to relay mail through Postfix, and the smtpd_relay_restrictions parameter to permit_mynetworks. This will ensure that Postfix will only relay mail from the trusted internal hosts, and reject mail from external hosts unless the sender is authenticated or authorized. For example:

mynetworks = 192.168.0.0/24, 127.0.0.0/8 smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, defer_unauth_destination

The other actions would not help prevent the mail server from being used as an open relay, or they would affect the functionality of the mail server. Configuring Dovecot to support IMAP connectivity would not affect the SMTP relay, but it would allow users to access their mailboxes remotely. Configuring netfilter to not permit port 25 traffic on the public network would prevent the mail server from receiving any mail from the outside world, which would defeat the purpose of having a mail server. Upgrading the mailbox format from mbox to maildir would not affect the SMTP relay, but it would change the way the mail messages are stored on the disk.

References:

• LPIC-2 Exam 202 Objectives, Objective 205.3: Managing a postfix server
• Postfix Basic Configuration, Postfix Documentation
• Postfix SMTP relay and access control, Postfix Documentation
• How to disable open relay on Postfix? - Howtoforge, Forum
• Postfix SMTP relay without authentication | Guide - Bobcares, Blog