What is external DNS?

What is the difference between a Primary and an authoritative DNS server?

• Hi, I'm studying for the MCTS 70 640 exam which assumes a level of background knowledge about DNS that I seem to be lacking and I'm struggling to find a good source of information. One point that I'm stuck on is this - an authoritative DNS server is one that has a complete zone file. So then I read about primary DNS servers and I've read statements like "A Primary DNS Server is the authoritative source of all information for a domain". So what is the difference? Can anyone point me toward a clear over view of what the different servers (Authoritative, Primary/Secondary, Master/Slave). Thanks

• Answer:

  To answer your question, they are in fact one in the same, however, most people refer to your primary server as the first one configured on a system to do name lookups and secondary as a backup on the same system in case the primary is unavailable. An authoritative NS is one that actually hosts the zone file for a domain, so this is refereed to as authoritative for the domain because all the information is actually configured there by a sys admin and all lookups for that domain will go there. If you do a whois lookup for a domain, you will see the authoritative NS for that domain listed there, this is where the Internet name servers go to resolve hosts lookups for that domain.