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Rackspace Cloud Essentials 6 - Creating a Reverse DNS Record

  • Article ID: 64
  • Last updated on August 13, 2012
  • Authored by: Rackspace Support
  • (22 Comments)

NOTE: This article is written for our First-Generation Cloud Control Panel.

Why Reverse DNS Lookups?

Reverse DNS records are an essential setting for those running a mail server since many recipient servers reject, or mark as spam, all email that originates from an “unauthenticated” server.

This basically means that after the sending IP address is checked, if the Reverse DNS does not match the sending domain, then it is classed as “unauthenticated”.

We put ”unauthenticated” in quotes because having a Reverse DNS record attached to your domain does not automatically guarantee acceptance of email originating from your domain by the recipient's email server. It's just that non-matching or generic reverse DNS lookup (RDNS) settings are often rejected out of hand.  Having a Reverse DNS record for your domain will prevent email originating from your domain from getting immediately rejected.

RDNS can also be very useful  when tracking down network issues and was the original driving force of RDNS. When pinging a website or IP address, one part of the output is the server's RDNS record.

 

How Does it Work?

When you enter a domain name into your browser, the DNS system will find the IP address of the server the domain is associated with.

A reverse DNS lookup does the opposite. It establishes what domain is associated with the IP address. This is a useful setting to configure for anyone but essential for customers running a mail server on their Cloud Server.

 

How Do I Set this Up?

You can easily set up reverse DNS  through the control panel. Just perform these steps:

  1. Log in to your Rackspace account.
  2. Click the Hosting menu item on the left.
  3. After that drops down, click Cloud Servers.
  4. This presents you with an overview page of your Cloud Servers. Click the link for your Cloud Server.
  5. Click the DNS tab at the top. This is where you  modify your DNS records.

6.  Scroll down to the section  called Reverse DNS Management. You will see your IP address for that server listed. Click the hostname under the DNS Record column.

7.  A window appears and asks you for the hostname that you would like to set it to. After you enter your hostname, press Update. This change is immediate.

8.  Simply entering the hostname of your server will not be enough.  Your hostname needs to be a Fully Qualified Host Name (FQHN) that is set for a domain that you control.  You will see the red square next to the DNS Record field change to green when an FQHN has been entered.

 

Now that you know how to make changes to your DNS configuration, we're going to teach you a useful way to check your settings using the dig command.



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22 Comments

what if we have 2 different domains in same server and we want to use 2 different mail server. eg. mail.domain1.com, mail.domain2.com. How can we use reverse dns?
By Anonymous on Aug. 1, 2012

Yes, you can use RDNS with that setup, but both domains will need to use the canonical name of the mail server in the MX record. In other words, both domain1.com and domain2.com might need to use "mail.domain1.com" as their mail server address. If you don't want an obvious link between domain1 and domain2 you might use a third domain for the mail server, as in "mail.domain3.com".
By jered.heeschen on Aug. 1, 2012

Hi

These instructions are for first generation cloud servers only. How do we do this on the 2nd gen servers?

Thanks

Simon
By Simon Brown on Aug. 26, 2012

I'm afraid the next gen control panel doesn't support reverse DNS lookup configuration yet. You can only configure reverse DNS for next gen servers through our DNS API right now. Hopefully that feature will be added to the new control panel soon.
By jered.heeschen on Aug. 31, 2012

Can you only setup reverse DNS for a cloud server if you add a domain to the Cloud DNS service?

By Ewan McNab on Sep. 8, 2012

You can use the Cloud Control Panel as described in the article with a first-generation Cloud Server. If you create a next-generation (open cloud) server, you would have to use the API for now to configure its rDNS.
By jered.heeschen on Sep. 10, 2012

Two questions regarding this - are rDNS records being created at all for next generation Cloud Servers right now? And can you please point to a specific API documentation about querying the rDNS records for next gen Cloud Servers?
By Martin Tajur on Sep. 14, 2012

Offhand, I'm not sure if default rDNS records are being created for next-gen servers. I'll try to find out. You can manage rDNS for next-gen servers using our DNS API. The documentation is here:

http://docs.rackspace.com/cdns/api/v1.0/cdns-devguide/content/ReverseDNS-123456999.html
By jered.heeschen on Sep. 26, 2012

I have set up reverse DNS for my host's public IP address. I have some services running between my other hosts using the service network and for authentication purposes I would like to have reverse DNS for the service network IP addresses for my hosts. Is this possible?

Regards, Miles
By Miles Gillham on Oct. 4, 2012

I don't think it's possible without setting up your own DNS server, Miles. The private network uses IP addresses that are reserved for private networking, so public DNS servers wouldn't be able to serve up meaningful PTR records for those addresses.
By jered.heeschen on Oct. 9, 2012

Hi, I'm setting up websites on my Rackspace server, and I'm using a third party software (ISPConfig) to manage my own two nameservers and DNS records. I want to add reverse DNS to the mix. Do I need to do that from my Rackspace control panel, or should it be possible to do it from my own nameservers? I ask because I have the .in.addr.arpa zones set up, but they don't seem to be being found correctly and I was wondering if I'm going about it wrong.
By Joe Miller on Oct. 19, 2012

You would need to manage the reverse DNS from our control panel (or the DNS API). Since Rackspace is the owner of the IP addresses, the Rackspace name servers are what would be consulted by anything doing a reverse DNS lookup or those addresses.
By jered.heeschen on Oct. 22, 2012

I'm disappointment with the situation that I have to whip up an API call just to add a PTR record in my DNS. This is the second "feature" that failed to make it over to the second gen servers, the first one being the extra IP address for multiple SSLs. I'm still ticked about losing the awesome CloudKick interface. APIs are great and I use them all the time, but dangit guys, you're taking our front end GUIs and replacing them with APIs instead of just adding an API.

I may be just griping but you've made a quick 60 second fix into an hours worth of work. Perhaps you should list all the features that DID NOT make it to the second gen platform so I can be more informed at to whether I will use the platform.
By Snapper Morgan on Oct. 30, 2012

Hey Snapper,

Sorry for the frustration. I'll be sure to forward this feedback to a product manager for review.
We do have a First-Gen and Next-Gen chart comparison here: http://rax.io/JS7s
Bookmark that page for future updates.

Best, Rae
By Rae D. Cabello on Nov. 2, 2012

Hi there.
Is there anyway to check the rDNS using nova?
Thanks
By Eric on Nov. 6, 2012

Not at this time. We are still working to get rDNS into the newer control panel for next-generation servers, but I can't say when it will be available. Until then I do recommend sticking with first-gen servers if you need rDNS and don't want to manage it via the API.

We do offer a feature that lets you take a snapshot of a first-gen server and use that snapshot to make a next-gen server. That means you can make a first-gen server for now and migrate with little fuss once the features you need (like rDNS) are available for next-gen servers.
By jered.heeschen on Nov. 6, 2012

For all Next Generation users, I just stumbled across this: http://www.toodlepip.co.uk/blog/2012/11/setting-reverse-dns-rackspace-next-generation-cloud-servers
By Adam on Nov. 29, 2012

https://github.com/cloudnull/ptrcreate

It took under 1 minute to create new PTR records for one of my domains!
By Adam on Nov. 30, 2012

The script linked here worked great for me. Can't believe something this basic isn't in the control panel since it was in the old one. At a minimum at least put a note in the control panel to contact support to have them do it for you.
By Brad on Jan. 3, 2013

Thanks to Adam for the link, and to the script author.

Somewhat amazed that Rackspace thinks this is good enough.
By Tom on Dec. 30, 2012

No, it's definitely not good enough. We are working on getting reverse DNS into the next-gen control panel, but it's not yet ready for prime-time. Unfortunately, in the meantime the Cloud DNS API (and excellent scripts like that one that use it) are the only option.
By jered.heeschen on Dec. 30, 2012

Reverse DNS is now available in the new control panel for both next-gen and first-gen servers. We'll add an article detailing it soon.

You can find reverse DNS controls by going to a Cloud Server's details. In the first "Server Details" section is a line for reverse DNS that has options to view, modify, or delete the PTR record(s) for the server.
By jered.heeschen on Jan. 22, 2013

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