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windows - Explain output of ipconfig /displaydns


Can you please tell me what each field of the Windows command



ipconfig /displaydns



means please?



Answer



The fields in the output of /displaydns correspond to the fields of an actual DNS reply.



  • In a DNS server's database, each piece of data is a "resource record".

  • "Record name" is the name you query DNS for, and the records (addresses or something else) belong to that name.

  • "Record type" is the type, displayed as a number - although more commonly they are referred to by their names, internally (in the DNS protocol) each has a number. Type 1 is "A" for "address", an IPv4 address. (IPv6 uses type 28, "AAAA", for an address four times as long.) "PTR", type 12, is a "pointer" to a hostname - most commonly used when mapping an IP address back to its name. "CNAME" is "canonical name".

  • "Time To Live" is the time in seconds after which the cache entry must expire.

  • "Data Length" appears to be the length in bytes - an IPv4 address is four bytes, IPv6 is sixteen bytes. For CNAME or PTR, Windows displays a static number (either 4 or 8, depending on your system) - this is actually the size of a memory address where the actual text is kept.

  • The "answer" section of a DNS reply is the actual answer to the query, and "additional" contains information that will likely be needed to find the actual answer. For example, glue records.

  • " record" shows the actual value stored.


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