Learning Action in publishing DNS part 6

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Learning Action in publishing DNS part 6 Chapter 4In this case the default domain is modified according to the value stated as the first parameter ofthe $ORIGIN command.If a relative name is stated, it is changed into a complete name by adding the domain specified inthe SOA record or defined by a parameter of the $ORIGIN command that precedes the databaserecord. The $ORIGIN command then changes the default domain.If the default domain is not changed by the $ORIGIN command, the domain from the SOA record isused. If the SOA record has the @ symbol instead of the domain, the first parameter of the primaryor secondary command from the etc/named.boot file is used.4.2.10 $INCLUDEAnother file can be inserted into the source file on the disk using the following command:$INCLUDE fileThe file is inserted in the same location as a command. It is also possible to state:$INCLUDE file default_domainThis way you both insert a file and change the default domain. The change in the default domain isonly valid for the lines of the inserted file.4.2.11 Asterix (*) in a DNS NameWe can use an asterix (*) as a wild card character in a DNS name. But how does an asterix work?Lets look at an example using an A record:*.company.com IN A 10.1.1.10DNS will answer any query about an item of the company.com domain not explicitly stated in DNSthat its address is 10.1.1.10, i.e., computer1.company.com has the address 10.1.1.10,computer2.company.com also has the address 10.1.1.10, and so on. Even if we want it to be so andif we make a mistake and write compter1.company.com instead of computer1.company.com, DNSwill not answer that we made a mistake, but it will give us an address, which is most likely to bea different address to the one we would have expected. Throughout the book, we have consistently tried to avoid the use of an asterisk in domain names. Our experience has proven that the use of an asterisk in domain names lead to unexpected errors. Therefore, they are only used in MX records, and they might be used in the future for SRV records.4.3 Name Server Implementation in BINDThe format of individual records in DNS databases was established by the BIND system. Nameservers appeared later, but the original DNS database format remained unchanged. Windows 2000also uses this format. (Of course, if Windows 2000 stores primary text database files into theActive Directory, everything is transformed into the standard format of Active Directory.) 89Name Server ImplementationFirst, let us examine version 4 of the BIND system, which should not be ignored.4.3.1 named Program in BIND Version 4 SystemThe name server of the BIND system is implemented by the named program. We are now going tofocus on version 4, which is easy to understand and forms the basis of the succeeding versions.The configuration of this version is very simple. It is also recommended for administrators ofWindows 2000 networks to familiarize themselves with this version because the name serverimplemented in Windows 2000 server can be operated not only by using Windows, but also byediting configuration files, whose format is based on the BIND system version 4.The named program first reads the named.boot configuration file at startup. At startup it also readsthe DNS databases from the disk and loads them into the cache memory according to instructionsspecified in the named.boot file. By default, the named.boot configuration file is located in the/etc directory. Any different location of the configuration file must be specified by a parameter inthe command line starting the named program. The named.boot configuration file contains thefollowing commands: • directory:Specifies a directory on the disk, where the DNS databases are stored. Within commands, the names of files are specified without their paths. For example: directory /etc/namedb • primary: Specifies that the name server will be the primary name server for the zone stated as the first parameter in the command and the relevant database is in the text file stated as the second parameter. For example: primary company.com db.company.com Every name server (including caching-only name servers) must be a primary name server at least for the 0.0.127.in-addr.arpa domain. For example, even when caching the name server, only the configuration file must include a command such as the following: primary 0.0.127.in-addr.arpa db.0.0.127 • secondary: Specifies that the name server will be a secondary name server for the zone specified by the first parameter. The following parameters (must be s ...