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Why Do We Need Four DNS Servers?

Occasionally, we see a perplexed blog owner asking a popular question about custom domain setup.
Does my domain really need four servers?
Some even seem to think that newer domains, with less readers, can get by with less - even one - servers.

Won't one server do - at least, for newer blogs? Theoretically, yes. But not one server is going to be 100% reliable, or last forever. Every computer ever made, like every human born, will die, one day.

Your blog (and your domain) depends upon DNS, to resolve its address. Address resolution is an essential part of helping your computer (your readers computers) connect with the computer where your blog is stored.

If you specify just one server for your domain, and that one server goes down, your domain will be out of service.

With a single name server used, the domain may be online to you, right now.

Just because the domain looks OK, to you, right now, that does not mean that it is OK, to everybody else - or that it will remain OK, next week.

The named DNS server "ghs.google.com", that provides addresses for the published URL, is a redundant server array.

www.mydomain.com. 3600 IN CNAME ghs.google.com.

We use "A" records to address the domain root, consistently.

We use a "CNAME" to reference "ghs.google.com" - though we can't always use a "CNAME". Some registrars will not let you use a "CNAME" to address the domain root.

Google provides the 4 x "A" addressed server set. These servers are used to address the domain root - when you wish to simply redirect the domain root to one of the aliases - or when your browser or computer uses the domain root.

Most domain owners will redirect the root to the "www" alias - though you are allowed to redirect to any one alias, at your discretion.

Redirect mydomain.com to www.mydomain.com

Google provides the 4 servers, to give us multiple redundancy.

Google provides four mutually redundant individual servers, each responding to a specific IP address, for custom domain clients to access in a round robin sequence.

mydomain.com. 3600 IN A 216.239.32.21
mydomain.com. 3600 IN A 216.239.34.21
mydomain.com. 3600 IN A 216.239.36.21
mydomain.com. 3600 IN A 216.239.38.21

Here. we see the mysterious 4 x "Points to" values (for GoDaddy) - and similar labels ("Destination", "Target") used by various other registrars.

If 1 of the 4 "A" addresses servers is not responding, another is used.

If any one server in the array of four becomes overloaded or goes out of service, and doesn't respond to a DNS query, the DNS resolver, on any client computer, will try the next server defined - if there is another server provided.

If your domain provides just one server to resolve its address, and that one server goes down, your domain goes out of service. Your readers will see, yet again

404 Server Not Found

But wait - - there's more. Since Google provides four servers, and only one is out of service, they won't regard that as a major emergency. They still have three servers online - and nobody is losing sleep. Except, of course, you.

Google will repair or replace their one down server, when it is convenient to them. Maybe that will be next week, when their DNS server technician gets back from vacation.

Is that not convenient to you? Sorry.

With 4 x "A" addressing, you can't publish to the domain root.

With an asymmetrical configuration, you may not publish to the domain root. Your only valid choice is to publish to "www.mydomain.com", and select "Redirect mydomain.com to www.mydomain.com". If you publish to "mydomain.com", you will eventually see

Another blog is already hosted at this address.

or

Blogs may not be hosted at naked domains.

or maybe

Key already exists for domain (your domain URL).

If you see any of these, your domain may require more extensive work.

If you want to publish your blog to a custom domain using an ASymmetrical configuration, always publish to "www.mydomain.com" - not to "mydomain.com". If you want to publish to "mydomain.com", you'll have to use a Symmetrical DNS configuration - and risk losing services hosted by your registrar.

You need to use all 4 servers, for domain stability.

If you go with the first option, you will need all 4 servers - if you want a reliable and supported custom domain. Note that "different" / "more" is not always "better" - and different / more servers will make your domain unstable.

If your registrar or hosting service does not support 4 x "A" DNS addresses setup, you may want to use a (free) third party DNS host. Now, here's hoping that your registrar allows easy configuration of third party DNS service.

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