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Wouter Kobes
49 lines
2.3 KiB
Markdown
49 lines
2.3 KiB
Markdown
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 anything 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 anything else.
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* Record does not start (left side) with _ or -.
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# MX
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* Used to specify a mailserver.
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* Contains a hostname, which in turn points to one or multiple A and/or AAAA records.
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* Preferably 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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* Redirects to other DNS name with its own records (A, AAAA, CNAME).
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* Be careful with CNAME chaining; don't use too many CNAMEs in a row.
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# CAA
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* Used to allowlist Certification Authorities that may issue certificates.
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* May contain several policies, like issue, issuewild (wildcard, i.e. certificates valid for all subdomains), issuemail (S/MIME certificates) and issuevmc (BIMI certificates).
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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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* Used to specify a nameserver.
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* Contains a hostname, which in turn points to one or multiple A and/or AAAA records.
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# SOA
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* Mandatory for every DNS zone.
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* Contains the following information (separated by a single white space):
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* FQDN of the primary 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 and other dots escaped using a backslash).
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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 primary 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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