22
Jan
10

Getting an Authoritative Answer from DNS


This page describes the process of getting an Authoritative answer from DNS.

Typically when you do a DNS lookup you would see something like this…

nslookup yourdomain.com
Server:  some-random.dns.server.com
Address:  xxx.xxx.xxx.xxx

Non-authoritative answer:
Name:    yourdomain.com
Address:  xxx.xx.xxx.xxx

As you can see from the highlighted line that this is a non-authoritative Answer. This means exactly what it says. The answer came from a name server that is not the authoritative source. This can either be from cache or the server had to relay the query another server. Once it obtained the answer it returned it back to you as a non-authoritative answer.

To get an authoritative answer do the following:

  1. Get the name server responsible for your domain
  2. Query the name server directly.

Getting the Name Servers Responsible

nslookup -querytype=NS yourdomain.com
Server:  resolver
Address:1.opendns.com  208.67.222.222

Non-authoritative answer:
yourdomain.net	nameserver = ns51.yourdomain.com
yourdomain.net	nameserver = ns52.yourdomain.com

Query The Name Servers Directly

Pick from one of the name servers that get returned. In my case I picked the second one.

nslookup yourdomain.net ns52.yourdomain.com

This time around you should not be getting a non-authoritative answer.

A better way would be to run the dnsq command.


dnsq mx yourdomain.net ns52.yourdomain.com

Doing a Reverse lookup

In ubuntu you can run the “host” command passing in the hostname or ip address. You can also type host -t MX to find the Mail exchanger record. The type argument value can be any recognized query type: CNAME, NS, SOA, SIG, KEY, AXFR, etc.

example:

prompt> host -t MX silverflix.com
silverflix.com mail is handled by 0 mx.silverflix.com.

Setting up an MX record

In the tinydns configuration file just prefix the record with “@”.

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