Sujets > Network

How DNS works ?

DNS servers, resolvers, nameservers, dig

Describe the flow of communication when visiting a domain like whatever.com ?

Browser -> Function -> Resolver -> Authoritative Nameservers

  • browser uses DNS to look up IP addresses
  • operationg system provides function to do DNS lookups
  • function sens requests to a server called resolver which know where to find authoritative nameservers
  • authoritative nameservers are servers where DNS records are stored

NB: There is DNS cache at every step

What are the 3 levels of the authoritative DNS servers ?

example : julienrollin.com

  • root : delegates to .com nameserver
  • .com nameserver : delegates to julienrollin.com nameserver
  • julienrollin.com anwsers with IP for julienrollin.com

List of root servers (very few) : https://root-servers.org/

Which tool to list details of DNS ?

dig julienrollin.com

Only record

dig +short julienrollin.com

Show how domain is resolved begining at root server

dig +trace julienrollin.com