DNS and what to watch for

Trev’s suggestions on the best way to manage your domain name

Domain names are a vital part of your hosting and mail system and is often forgotten as it’s the part that sits in the background quietly working until one day it does not. This is meant as a plain english guide to help would be web masters understand how to set up the management of their domain name to reduce the impact of outages on the internet.

First, what is DNS

DNS stands for Domain Name Service.

Human’s like to use names. A name has a meaning. The internet can’t use names, it needs numbers. So we have an issue.

DNS is the translator between the human name and the internet number. So my web site here is called “trev.id.au”. That’s what you type in your browser to get here. Your web browser asks the DNS for trev.id.au internet number address. The DNS returns the number (in this case The browser now can ask the networking system of your computer to go fetch the page for the address that the Internet can work with.

Email works in a similar manner. You address an email to user@domain.com.au. The email program first asks the DNS where it should send mail for domain.com.au and what is the number address or IP address. It then tries the address and if it works, it sends the mail.

The key problem with incorrectly managed domains.

The real problem is around email. If an email server cannot resolve your domain name because the DNS is down, it will return the email to the sender with an error that makes it look like you don’t exist. If it’s just a hobby system, not so bad, but if it’s your business, it can be severely damaging.

What needs to happen

You should have at least two physical servers in different parts of the internet doing the resolution of your domain name (the translating between name and number and the telling where to send mail). It’s also a good idea for these servers to be different from your domain name registrar and your hosting provider. I have used both http://www.zoneedit.com and http://www.dyndns.org.

So with two seperate servers capable of answering DNS queries for your domain and email, and these in two different physical locations, both have to be down for your domain to be down. Chances, well I’ve been hosting this way for about 7 years now. My site goes down because my server does, but my domain has never and mail always works.

You can host the domain name at zoneedit for free on 2 servers (as per their site at time of writing this)

Email when your server is down

Servers go down. That’s life. What happens to email if your server is down? If the domain name resolves, the sending mail server will generally hold and keep trying for a short while. This overcomes the occasional network outages. For longer periods, the sending mail server bounces the mail back to the sender.

This can be overcome by using a mail forwarder which is a server on the internet that is defined as being the second server if the primary server is not available. It holds a lower priority than your main mail server. This allows your server to go down with no impact to mail from the outside world.

I use this service and have been happy to pay the small amount it costs me each year.


Separate functions to provide resilience.

1. Register the domain name with a domain registration authority. Seehttp://www.auda.org.au/registrars/accredited-registrars/ for a list. I’d recomend using a AUDA accredited organisation.

2. Register with a DNS hosting organisation like www.zoneedit.com or www.dyndns.org and set up your domain name. Note this is not registering the name, but it’s getting it ready. You will be given some info from the DNS hosting company in the form of a name and ip address for each of the two servers that are going to host your domain name.

3. With the server information, go back to the registrar and manage your account/domain. Find where to enter the domain name server information and change it to the names and ip addresses provided in step 2.

4. Now sign up with a hosting company. The hosting company will give you an IP address to use for your domain name. You should use the manage interface of the DNS hosting organisation to configure the name and number for domain.com, www.domain.com and optionally, but usually good, mail.domain.com. These 3 names should all point to the IP address provided by the web hosting company in step 3.

Detailed configuration example
[This is under construction]

There are many providers of these services. I’m going to provide the detail around setting this up using www.enetica.com.au as the Domain Name registrar, www.zoneedit.com as the DNS hosting organisation and www.mdwebhosting.com.au as the web and mail hosting company.

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