DNS Domain Name System

DNS Domain Name System

Like a phone book for the internet  name <—> numbers


Domain namespace similar to filesystem structure


domain name system

A  Address

NS name server

SOA authority

PTR pointer

MX mail efer


Name Server

  • holds info about structure of tree& resource records
  • every domain has authority name server
  • can cache info so repeated look-ups are fast


  • programs that track down RR’s
  • Know how to contact root name servers and follow chain until find auth. name server
  • 13 root name server     a.root-servers.net


dig  @k.root-servers.net www.wwu.edu  A +norec


dig command8 authority

dig command additional section

dig @g3.nstld.com www.wwu.edu A +norec

dig g3


Reverse DNS – to verify integrity of message


rpm -qa bind*


/etc/ named.conf

It works as a caching only name server without modification.

/var/lib/named #   more localhost.zone


TTL time to live –

localhost 127