Fun with DNS: Three Useful Commands

The DNS is a distributed, hierarchical database where authority flows from the top (or root) of the hierarchy downward.

When thinking of the structure of the DNS, imagine an inverted tree. Each branch of the tree is within a zone of authority; however, multiple branches of the tree can be within a single zone.

The software (Bind being the most common) that stores domain name information is called a domain name server. A single name server can be authoritative for multiple zones. All zones have a primary master and a secondary master name server that provides authoritative responses for their zones.

If you query a name server not authoritative for a particular zone, that name server will most likely have up-to-date information. This is because zone information propagates throughout the Internet at regular intervals, and name servers cache zone information for which they are not authoritative.

DNS Commands

There are three crucial commands that can put all the DNS information you need at your fingertips. The way to use this article is to try each of the commands listed on a domain name, so you can see what the output looks like. Learn by doing!

Zone file database records divide DNS information into three primary types: NS (Name Server) records, MX (Mail Exchange) records, and A (Address) records. NS records indicate the name servers. MX records indicate the hosts that handle e-mail delivery; the priority (pri) number indicates the order in which mail servers are used, with the lowest number receiving the highest priority. The A (Address) records map hostnames to IP addresses, the real names of machines.

host

This is the simplest of the DNS commands. It is a quick way to determine the IP address of a hostname:

: host www.your-domain-name.com

The -a option will return all of the DNS information in verbose format.

: host -a www.your-domain-name.com

Now that you know the IP address for www.your-domain-name.com, try a reverse lookup.

: host IP-ADDRESS

dig (domain information groper)

This command gathers and returns DNS information in a format the name server can use directly. You will find it easy to query specific name servers with dig.

You can quickly determine the Name servers of your host or any other host:

: dig ns your-host.com

Then you check your (or another) website against the host's name servers:

: dig www.your-domain-name.com @ns.your-host.com

Dig can provide output that is in the same format as the zone file itself. Here is how to get the whole zone file:

: dig any your-domain-name.com

Here are the most useful dig query types: dig any (gathers all DNS information), dig ns (gathers name server information), dig mx (gathers mail exchanger information) and dig a (gathers network address information).

The dig command can also do reverse lookups with output formatted for the zone file:

: dig -x IP-Address

nslookup

You can use this tool as a single line command, or you can use it interactively, which distinguishes it from the other DNS commands. Once you have started nslookup, type set all to list the default options. As with dig you can choose the server (name server) you want to query, and you can decide the type of DNS information on which to focus.

Just as you can issue commands to nslookup interactively, you can also change the initial defaults by starting a .nslookuprc file. The format of the .nslookup is one command per line:

set type=NS
set domain=srvns.your-host.com
set timeout=10

Conclusion

These three commands can provide you with most of the information you need about your domain names. They are powerful tools, and this article should provide you enough information to get started or offer a quick refresher if you already use these commands.

About the Author:

Dan Forootan founded EZ Publishing, Inc. in 1998. EZ Publishing's Small Business Web Hosting provides the essential tools for using the Web as a marketing tool. The package includes web hosting, the StreamSend permission-based email marketing solution. Please email questions or comments about this article to articles@ezpublishing.com. Thank you.

---

4 Critical Things To Look Out For In A Web Hosting Service

1. The reputation of the web hosting company.Most web hosting... Read More

A Simple Guide to Web Hosting

Personal Computers, Servers Or ISP?You need a server to host... Read More

Choosing a Quality Web Host

If you are anything like me, you'd probably like to... Read More

Best Web Hosting Company - Find The Most Affordable Host

If you're creating a community web site or a business... Read More

Good Web Hosting ? What Is It?

With hundreds of web hosting companies to choose from today... Read More

Transferring Your Existing Website to a New Hosting Provider

You've already got a website, but your current hosting provider... Read More

Hosting Your Own Web Server: Things to Consider

Are you disgusted or disappointed with your current web host?... Read More

Web Hosting Services Absolutely Necessary for Your Websites Success

Web hosting services play a vital part in your website's... Read More

Switching Web Host

Moving a web site to a new host is not... Read More

Avoiding Bad Web Hosts

The Internet represents the most powerful communication revolution since the... Read More

Managed Vs. Unmanaged Dedicated Hosting

"Unmanaged dedicated servers" - this is a pretty uninviting term... Read More

How to Choose a Hosting Web Package Cheap

If you're looking for a hosting web package cheap there... Read More

Dedicated Web Hosting Explained

Why is dedicated hosting such a big hit on the... Read More

How To Change Your Web Hosting Provider ? Step-By-Step Guide

Whether you are disgruntled with the level of service your... Read More

Free Web Hosting - Why Might It Be A Bad Idea

When talking about free anything the legitimate question that first... Read More

How to Choose a Right Web Hosting Service?

Indeed, choosing a right web hosting service for your website... Read More

Choosing a Web Hosting Provider from 40 Million Other Web Hosts - Pt1

Discover how to go about choosing a web hosting provider... Read More

Cheap Web Hosting ? Choose The Right Company

You have carried out the hard part and that's creating... Read More

How to Choose a Web Host - Frequently Asked Questions

In this article you'll be provided with helpful information about... Read More

Adult Web Hosting: The All You Need To Know

What sort of web hosting options should you go for... Read More

4 Tips to Find the Web Host That?s Right For You

Choosing to make a web site is a very big... Read More

How You Pay More for Unused Web Space and Traffic

"2GB web space with 50GB traffic for $5.95 per month!"A... Read More

Sender Policy Framework (SPF) ? How to use it to Fight Email Forgery

Spam is a real problem today. Forged email is a... Read More

Thinking About Changing to a New Web Hosting Company? 5 Steps to Plan Ahead for the Move

Perhaps your web hosting company has a technical support group... Read More

Website Sitebuilders: Easy to use Website builders Come with a Price

Professional web designers don't come cheap. A good web designer... Read More

Webhosting for Blogs - Free or Paid Service

Blogging is an abbreviation of "web-logging". The simplest definition of... Read More

Small And Medium Businesses Embrace Servers Running Linux

Although we are aware of Linux adoption by large enterprises,... Read More

Dedicated Server vs. Co-location Web Hosting

So - you know shared hosting no longer cuts it,... Read More

Choosing the Right Web Host

Whatever type of website you want to host, choosing the... Read More

Monitor Your Web Site for Downtime

For those in the Internet business the availability of their... Read More

How to Find Good Web Hosting for Your Site!

When building your first site the main things that you... Read More

The Top 15 Essential Ingredients of Every WINDOWS HOSTING Plan (Package)

First things First. Why would you like to have Windows... Read More

How To Choose A Web Host That Meets Your Needs

One of the most difficult choices you have to make... Read More