Free Dynamic DNS Service Subdomain HowTo

There is a new free non-profit Dynamic DNS (DDNS) service which can be used as free alternative for subscription based services like dyndns.org or no-ip.com. The provider website is, at the time of writing, only in German but the setup is very simple and explained step by step below.


The article will explain
  • What is Dynamic DNS (DDNS)?
  • How to get your free subdomain as myhomepc.ddnss.de in two minutes?
  • How to configure your router to update your IP address?
  • How to make your PC available from the Internet with Port Forwarding?


Dynamic DNS (DDNS)

DDNS, in the context of this article, is a way to easily update the IP address which belongs to a subdomain. It allows a device to be reachable under a fixed subdomain while the IP address may change from time to time. The update of the IP address with the subdomain hoster is usually performed automatically by the router.
When the IP address is updated, then anybody that is connected to the internet, can run a Nameserver lookup (NSlookup) or Ping request for that subdomain and the IP address is returned.


Get your free subdomain in 2 minutes

Go to http://www.ddnss.de/user_new.php. Insert your data as shown in the following picture. The writing in black was added by me.
If there were no errors then the next page will say that registration was successful and that an E-Mail was sent to the address you provided. Check your mail and click the "Aktivieren" button as shown in the following picture.
Now a web site opens that says "Dein Account wurde aktiviert" which means the account is activated. You can now login here http://www.ddnss.de/login.php.
When you are logged in, click the two icons, as displayed in the following picture.
Then choose your subdomain and click "Weiter". The checkmark or cross next to the button indicates if the subdomain is available or not. See the following picture.
Finally accept the default values on the next page by clicking on the "jetzt erstellen!" button.
Congratulations, you now have a subdomain. Read in the next section, how to let your router update the IP Address that the subdomain points to.


Configure your router to update your IP address

To connect to your router, type the router IP address in your browser's address bar. If you do not know the IP, then you can execute ipconfig in Windows to get the value of the "Default Gateway". The Default Gateway IP, in a home network, is usually also the router IP.
Go to the site in your router's menu where Dynamic DNS can be configured. There insert the values as shown in the following table. The bold parts must be replaced with your subdomain, user name and password.

Update-URL: http://ddnss.de/upd.php?user=<username>&pwd=<pass>&host=<domain>
Domain name: YourSubdomain.ddnss.de
User name: YourDdnssUserName
Password: YourDdnssPassword

Here is an example of my router configuration.


Make your PC available from the Internet with Port Forwarding

The above steps will enable you to access your router from the internet. However it is usually more interesting to access the devices that are connected to your router as your HOME-NAS via Browser, your Raspberry-Pi via Terminal, your PC via Remote Desktop Connection or your Home-Automation-Web-Interface via Browser.
Port forwarding basically means to define rules like "if a connection is made on my public IP on this public port then forward it to this private IP and this private port".
For example in the next screenshot you can see that I can access my Raspberry Pi via telnet (local port 22) from the public IP of the router and the port 9876. Using a different public port than the default adds some security and is one way to allow several devices to provide e.g. telnet from the same public IP.
In the next screenshot you can see how to add or edit a Port Forwarding rule with the FritzBox router.
Now you might think, that every device which is accessible from the internet needs a static IP address. But this is not the case. Defining a static IP address is usually just unnecessary work and it is also rather unsatisfying if you connect that device to a different network with different Subnet Mask because you cannot reach it. Instead you can use two features of your router. The first one is that the Port Forwarding rule is not defined to a local IP but to a local Computer name, as 'raspberry' in the screenshots above. So port forwarding still succeeds if the IP of the device named raspberry changes. The second feature that many routers support is to assign a given device always the same IP. This is not automatic but you must mark the devices in your router menu that should always get the same IP.
Lastly, a screenshot that shows the Fhem Home Automation Server accessed from the subdomain tmpd2.ddnss.de.