DNS Failover

As your business grows, it becomes more and more mission critical, and any amount of downtime is detrimental.  You could potentially lose thousands, if not tens of thousands of dollars for every minute your site is down.  Not to mention, it hurts your brand and customer confidence.  Don’t get nervous though, there is plenty that you can do to help prevent this from ever happening to you.

Having redundancy in place is key.  Traditional methods of redundancy and failover are an option, however, not the most efficient.  As your company expands and more servers are added to your network, a hardware solution becomes more complicated.  It requires a large upfront cost ranging anywhere from $25k to $150k on average, depending on what you want the hardware to do.  You are also adding a single point of failure into your network.  If that box fails, you better have redundancy on that box, which requires yet another large capital expense.  Then you have to pay to have those boxes maintained and replaced at the end of their life-cycle.  As you can see, it’s a pain in the butt.  So what’s another option?  “Does Not Suck” Failover, aka – DNS Failover  (little joke there)

DNS Failover Setup


DNS Failover is very easy to setup and the best performing option.   Pretty much all the major DNS providers today offer this functionality.  Just follow these simple steps to get setup…

1.  Choose a DNS provider that offers this functionality.  Almost all of them do, at least the good ones.

2.  After you sign up for DNS service, the provider will send you the nameservers that you should point to.  These will be the DNS servers of the DNS Providers network.

3.  Login to your registrar account, wherever you registered your domains.  (like GoDaddy, Network Solutions, EuroDNS, etc…)  Go to the section where you manage your domains and click on the DNS/Nameserver section.  This is where you’ll see the default nameservers for each of your domains (most likely the registrar’s nameservers –  for example – ns1.domaincontrol.com  for      GoDaddy ).  This is where you will plugin your new nameservers that your DNS provider sent to you.  Wait at least 48 hours before removing the registrar nameservers completely.

4.  Log back into your DNS provider account.  Import your domains into this account.  You can either do this manually for each domain, or you should be able to import/upload a zone file of all your domains (some registrars provide this).  Once your domains are setup in your DNS account, you’ll go to the failover section.  This is where you may want to consult your DNS provider for instructions, as it’s a bit difference for each provider.  Either way, that’s what they are there to do, help you. It’s not a hard process at all.  Essentially, you’ll choose the domain/record that you want to provide failover for (like mx.example.com, www.example.com, etc…).  You will then assign this record a primary IP address, and at least 1 backup IP address.  The DNS provider will monitor the health of your primary IP every X amount of minutes.  If your IP fails to respond, it will automatically failover to your backup IP.

Choosing a DNS Provider


Here are some very important items to keep in mind when choosing your DNS provider…

– Make sure you have very flexible control over your TTL settings at the record level.  This is your call, however, we don’t recommend keeping your TTL’s any higher than 5 minutes on your critical records.  Only you can decide how long you can be down for.  Remember, the TTL is how long your IP is cached for.  So if it’s cached for 5 hours, the fastest you’ll be able to failover to the backup IP is 5 hours.

– What type of probes/health checks do you want to do?  Standard is an HTTP get, but if you have other protocols like HTTPS, SMTP, FTP, etc…you need to figure out if the DNS provider has this option.

– Health check frequency:  When configuring the health checks against your IP, how often will this occur with your provider?  What’s the fastest you can set it for?  Think about it…if I’m only checking your primary IP once every 5 minutes, then 5 minutes plus whatever the TTL is set at, is the fastest the failover will occur.  We recommend no more than 1 minute.

– Manual vs. Automatic – Some providers will give the option to provide just the monitoring portion and then allow you to either setup an auto failover, and just simply alert you that your IP is down, and then  you can go in and manually failover.  Sometimes companies like this  feature for their own reasons.  It really depends on their environment and the type of content they are serving.

– Maintenance windows – this is not so important but a really cool and potentially helpful feature.   Some companies give you the ability to schedule a forced failover.  You would use this if you were planning to do maintenance of some kind and wanted to force a failover to an alternate server, while you do work on the primary.


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