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101 · Question #19

With standard DNS, assuming no DNS request failures, which process describes the normal resolution process on a "first time" DNS request?

The correct answer is D. Client requests address from LDNS, LDNS requests from root server, root server returns. Standard DNS first-time resolution uses an iterative process where the client queries its Local DNS server, which in turn walks up and down the DNS hierarchy to find the authoritative answer.

Section 1: OSI Model, Network, and Application Delivery Basics

Question

With standard DNS, assuming no DNS request failures, which process describes the normal resolution process on a "first time" DNS request?

Options

  • AClient requests address from root server, root server returns IP address to Authoritative DNS,
  • BClient requests address from LDNS, LDNS requests from GTM, GTM requests from Authoritative
  • CClient requests address from LDNS, Authoritative DNS receives request from root server, root
  • DClient requests address from LDNS, LDNS requests from root server, root server returns

How the community answered

(39 responses)
  • A
    3% (1)
  • B
    8% (3)
  • C
    3% (1)
  • D
    87% (34)

Why each option

Standard DNS first-time resolution uses an iterative process where the client queries its Local DNS server, which in turn walks up and down the DNS hierarchy to find the authoritative answer.

AClient requests address from root server, root server returns IP address to Authoritative DNS,

The client does not contact the root server directly; DNS resolution is iterative from the LDNS perspective, with the client only ever talking to its configured LDNS.

BClient requests address from LDNS, LDNS requests from GTM, GTM requests from Authoritative

This path describes an F5 GTM-assisted resolution flow and is not the standard DNS resolution process as specified in RFC 1034/1035.

CClient requests address from LDNS, Authoritative DNS receives request from root server, root

The authoritative DNS server does not receive requests from the root server; the root server only returns referrals to the LDNS, and the LDNS itself contacts each successive server in the hierarchy.

DClient requests address from LDNS, LDNS requests from root server, root server returnsCorrect

On a first-time DNS request, the client sends its query to the Local DNS server (LDNS). The LDNS, having no cached answer, queries a root name server, which responds with a referral to the appropriate TLD name server. The LDNS then queries the TLD server, receives a referral to the authoritative name server, queries it directly, receives the IP address, and finally returns the answer to the client - a process defined in RFC 1034.

Concept tested: Standard iterative DNS resolution hierarchy

Source: https://www.rfc-editor.org/rfc/rfc1034

Topics

#DNS resolution#LDNS#root server#authoritative DNS

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