What is rDNS? Setting Up Reverse DNS Lookup On SkySilk

Recently, you may have noticed a new input field when deploying a SkySilk VPS – reverse DNS (or rDNS for short). If you’re already familiar with forward DNS, the concept of rDNS shouldn’t come off as too complex. Although what might remain a fuzzy topic is the exact use for rDNS. First, it’s important to understand how reverse DNS works and why adding this capability to your server might come in handy.

How Reverse DNS Works: A Simple Metaphor

Let’s put the concept of reverse DNS lookup in terms of using a phonebook. Imagine you’re looking for the phone number of a gentleman named Mark. You would use a phonebook to look up Mark’s information given the specific name, thus retrieving his phone number. This is very similar to the concept of forward DNS in action. When you type in google.com to your address bar, the server returns the IP address associated with that domain.

Now its easy to conceptualize how reverse DNS works by thinking about this situation from the opposite perspective. Let’s say we have a phone number and now want to look through our phone book to find the name associated with that number. In other words, this is the action of looking up a hostname by their IP address.

how reverse DNS works


Setting Up Reverse DNS With SkySilk

In order for rDNS to work with your SkySilk server, you will first need to properly set up forward DNS. Part of this also includes owning a domain name which is set up using a domain registrar. Once this is complete, you can set up rDNS in one of two ways.

Deploy a Cloud Server

NOTE: rDNS is currently only available for our West Coast location. rDNS capability is currently in the works for New York and will be available soon.

  1. During the SkySilk server deployment process you will now see the option to add reverse DNS. Simply type in the hostname you want your IP address to resolve to (again, considering that the forward DNS rules are properly configured) and SkySilk will update the rDNS for that server.

        2. Once your SkySilk server is already deployed you will find a tab on the dashboard labeled “DNS Settings” (Note: this is for west coast deployments only for the time being). There will be an input field to set up rDNS for your IP address. Simply enter your hostname and hit Update. This will automatically update reverse DNS lookup information for your SkySilk server IP address. 

Reverse DNS Lookup – The Most Common Use Cases

Email Servers

There wouldn’t be many cases where you have an IP address and need to look up the domain name associated with it. This is why one of the main use-cases for reverse DNS lookup is with email servers. Typically used to avoid spam or phishing scams, email systems will assure that the sender (or in this case the IP address) can resolve a hostname. This is because those using bot (or zombie) computers can’t achieve validation. However, the method isn’t perfect. As recorded in 2003, AT&T WorldNet had to remove their filters as users were reporting that messages weren’t being delivered. This can be due to a variety of issues, mainly which revolve around zones.

rDNS Can Track Your Activity on the Web

Sounds like a marketers dream, right? Luckily tools like Google Analytics and a flurry of other independent companies can handle all of this data for us. Although, the main component that lies underneath it all is the reverse DNS lookup. Not only can rDNS help track location, but also the point of origin in which a visitor came from to end up on a specific page (which is a large factor in what makes Google Analytics so powerful). Now it may sound like an invasion of privacy, however, reverse DNS won’t expose any personal information, simply just data about the IP address itself.

Does my Server Need Reverse DNS?

Once you understand how reverse DNS works it can be a valuable tool for any server owner. As stated above, rDNS is especially important when it comes to mail servers. If you happen to be running your own email server without any rDNS, it is likely any and all of your messages will be filtered out and seen as spam. In order to properly set up rDNS, you will first need to properly configure forward DNS records (See above seciton on setting rDNS up with your SkySilk server).

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