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Learning publishing DNS in Action Ebook_7

Giao thức DNS làm việc với một số loại hoạt động. Các hoạt động được sử dụng phổ biến nhất là một QUERY DNS. Đó là một truy vấn mà cho phép có một hoặc nhiều hồ sơ từ cơ sở dữ liệu DNS. | Chapter 4 forward This is not a real zone but a method for forwarding queries on a per-domain basis. The name server has the role of a forwarder for the forward zone. A zone statement of type forward can contain a forward and or forwarders statement which will apply to queries within the domain given by the zone name. The name of a zone can be followed by a class. If the class is not specified in Internet is used. Parameters Most parameters of the zone statement have the same meanings as the parameters of the options statement with identical names. If a certain parameter is specified in the zone statement its value has a higher priority than the value of the parameter in the opti ons statement. allow-update This parameter defines those hosts that are permitted to carry out a dynamic update of the server. By default the dynamic update is prohibited from all hosts. update-pol icy This parameter provides the option to set rules for the dynamic update in greater detail compared with the allow-update parameter. The permission ban of a dynamic update can be set not only for the whole zone but also at a domain name level or for groups of names as it is in the case of the al low-update parameter. This parameter is only implemented in version 9 and higher. Only one of allow-update and update-policy can be used in the zone statement. 4.3.2.2 DNS Database BIND version 9 has also brought changes in zone files. Some of the most significant changes are the TTL and GENERATE statements. TTL Statement Every zone file must include either the TTL statement which defines the default TTL value for the particular zone or every RR record must include a TTL value. If this condition is not fulfilled the server announces an error during startup. BIND 8 was still able to use the TTL value from the SOA record. GENERATE Statement This statement is used to create an RR set that provides the reverse delegation of a subnet. Every DNS administrator who has at least once defined a reverse .