Network - DNS Lookup (Request|query)

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A DNS lookup is a request to a DNS server in order to translate a DNS name to an IP and vice versa.

Beware that not all DNS client are performing a lookup on the content of the host file as ping does.

Example of response knwon as replies

Each message consists of:

  • a header
  • and four sections:
    • question,
    • answer,
    • authority,
    • and an additional space.

A header field (flags) controls the content of these four sections

Example of A record query against

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 56993
;; flags: qr rd ra ; qd: 1 an: 2 au: 0 ad: 1 

; EDNS: version: 0; flags: ; udp: 512
;;, type = A, class = IN

;; ANSWERS:	300	IN	A	300	IN	A



;; Message size: 76 bytes



A forward lookup translate a DNS name to an IP. See What is a DNS Forward Lookup?


A reverse lookup translate a an IP to a DNS name. See DNS - rDNS - Reverse DNS (lookup|resolution) - from IP to name

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