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48 lines
2.2 KiB
Markdown
48 lines
2.2 KiB
Markdown
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This document lists the basic usage of commonly used DNS records. It can be used to track commonly made mistakes.
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# A
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* Points to an IPv4 address.
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* Does not point to anyhting else.
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* Record does not start (left side) with _ or -.
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# AAAA
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* Points to an IPv6 address.
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* Does not point to anyhting else.
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* Record does not start (left side) with _ or -.
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# MX
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* Points to an A and/or AAAA record.
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* Preferrably does not point to other record types, but the use of CNAME records is seen in practice. RFC's are inconsistent on this.
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* Has a priority value.
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# CNAME
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* Points to other records (A, AAAA, CNAME).
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* Be carefull with CNAME chaining; don't use too many CNAMEs in a row.
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* The end of a CNAME chain is always an A an/or AAAA record.
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* **Can only be combined with NS / SOA records if left side is equal.**
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# SRV
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* Records starts (left side) with _.
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* Points to an A and/or AAAA record.
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* Has a priority value.
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# NS
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* Points to an A and/or AAAA record.
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* **Used to point to subzones.**
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* **Used to indicate what is inside the parent zone.**
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* **Each zone needs this to indicate what is inside the parent zone as a reference to this zone.**
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# SOA
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* Mandatory for every DNS zone.
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* Contains the following information (seperated by a single white space):
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* FQDN of the primairy name server followed by a trailing dot.
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* e-mail address of the DNS administrator (followed by a trailing dot, the @ replaced with a dot).
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* an opening round bracket "(".
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* serial number that is changed (increased) on every zone change.
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* refresh time (in seconds) for a secondary name server to check the primairy name server for changes in the zone.
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* retry time (in seconds) for a secondary name server for requesting the serial number when the primary name server did not respond on the previous request.
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* expire time (in seconds) after which a secondary name server should stop answering requests if the primary name server is not responding.
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* Negative caching time to live (in seconds) which is the time a caching name server should cache a negative result (indicating that a name does not exist) coming from the authorative name server before trying again.
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* a closing round bracket ")".
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