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Packt publishing dns in action_2

Toàn bộ cơ chế này hoạt động nếu các địa chỉ IP của lớp A, B, C là chi nhánh. Nhưng những gì bạn nên làm gì nếu bạn chỉ có một mạng lớp C có liên quan? Bạn thậm chí có thể chạy máy chủ tên riêng của bạn dịch ngược lại? Câu trả lời là có. | Chapter 1 Figure 1.2 Reverse domain to IP address 195.47.37.2 This whole mechanism works if the IP addresses of classes A B or C are affiliated. But what should you do if you only have a subnetwork of class C affiliated Can you even run your own name server for reverse translation The answer is yes. Even though the IP address only has four bytes and a classic reverse domain has a maximum of three numbers the fourth numbers are already elements of the domain IP addresses the reverse domains for subnets of class C are created with four numbers. For example for subnetwork 194.149.150.16 28 we will use domain 16.150.149.194.in-addr.arpa. It is as if the IP address suddenly has five bytes This was originally a mistake in the implementation of DNS but later this mistake proved to be very practical so it was standardized as an RFC. We will discuss this in more detail in Chapter 7. You will learn more about reverse domains for IPv6 in Section 3.5.3. 1.4 Domain 0.0.127.in-addr.arpa The IP address 127.0.0.1 presents an interesting complication. Network 127 is reserved for loopback i.e. a software loop on each computer. While other IP addresses are unambiguous within the Internet the address 127.0.0.1 occurs on every computer. Each name server is not only an authority for common domains but also an authority primary name server to domain 0.0.127.in-addr.arpa. We will consider this as given and will not list it in the chart but be careful not to forget about it. For example even a caching-only server is a primary server for this domain. Windows 2000 pretends to be the only exception to this rule but it would not hurt for even Windows 2000 to establish a name server for zone 0.0.127.in-addr.arpa. 9 Domain Name System 1.5 Zone We often come across the questions What is a zone What is the relation between a domain and a zone Let us explain the relationship of these terms using the company .com domain. As we have already said a domain is a group of computers that share a common .