DNS and DHCP Servers – 19/Oct/2019


  • Purpose is to allocate ip address to Machines connected over the network

DNS Servers

  • Reference
  • Resolving name with ip address is major responsibility of DNS Servers.
  • DNS Servers are generally used for
    • Internal DNS Servers: These servers are maintained in your organization for internal name resolutions
    • Public DNS Servers: These servers are maintained by some organizations for internet domain name resolutions
  • Public DNS Servers Usecase:
    • We are running our application on AWS/Azure.
    • When we run in cloud we get public ip address.
    • To all external users, we expose applications by giving domain names
    • To get domain names, you purchase them from domain sellers (Go-daddy, hostinger.in)
    • We have to make Public DNs servers aware of our ip address

DNS Name Resolution

  1. Whenever you make a request, first name to ip resolution is checked in local hosts file (C:\Windows\System32\drivers\etc\hosts in Windows & /etc/hosts in *nix )
  2. The request will be made to root servers. Root servers respond with TLD server
  3. Request to TLD ns will result in ns
  4. NS will have a file called as Zone file which has records

Record Types

  • A or AAAA: Name to IP
  • CNAME: Alias record
  • PTR Record: inverse of A or AAAA
  • MX Records: Mail exchange servers
  • SOA:
  • CAA

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