tailieunhanh - Offer Packt Publishing Dns In Action_4

Tham khảo tài liệu 'offer packt publishing dns in action_4', công nghệ thông tin, cơ sở dữ liệu phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 4 In this case the default domain is modified according to the value stated as the first parameter of the ORIGIN command. If a relative name is stated it is changed into a complete name by adding the domain specified in the SOA record or defined by a parameter of the ORIGIN command that precedes the database record. 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 is used. If the SOA record has the @ symbol instead of the domain the first parameter of the primary or secondary command from the etc named .boot file is used. INCLUDE Another file can be inserted into the source file on the disk using the following command INCLUDE file The file is inserted in the same location as a command. It is also possible to state INCLUDE file default_domain This way you both insert a file and change the default domain. The change in the default domain is only valid for the lines of the inserted file. Asterix in a DNS Name We can use an asterix as a wild card character in a DNS name. But how does an asterix work Let s look at an example using an A record . IN A DNS will answer any query about an item of the company .com domain not explicitly stated in DNS that its address is . has the address also has the address and so on. Even if we want it to be so and if we make a mistake and write compter1. instead of computer1 . DNS will not answer that we made a mistake but it will give us an address which is most likely to be a 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 .