Dynamic DNS

Overview Experimental · Insiders only

Accessing your device from anywhere in your local network is great, but there are times when you might want it to be reachable from remote locations. This is particularly true for projects such as media servers, network attached storage (NAS) and VPNs such as those provided by RaspAP. However, due to the shortage of IPv4 addresses, it's likely that you will receive a new and different external IP address from your ISP each time your router is rebooted.

Some ISPs offer a static external IP address, although often at an additional cost above a basic subscription. This is where using a Dynamic DNS (or DDNS) service on your home network can be extremely useful.

Solution

Dynamic DNS solves this problem by providing a domain name that always points to the current IP address of your device, regardless of how often it changes. With DDNS, the IP assigned to your domain name is automatically updated by a piece of software (known as a daemon) running on your device. This means that you can access the server using the same domain name, without having to constantly update settings each time the IP address changes.

The daemon running on your device resolves your external IP address using one of several methods, then reports this to your DDNS provider. There are a number of different providers that offer Dynamics DNS free of charge. If you currently own a custom domain name, chances are your registrar provides DDNS or has a partner to support this.

Installation

The Quick installer will give you the option to add the required packages to your system, and enable the configuration page in RaspAP. Simply press Enter at the prompt to accept the default "Y" (yes) response:



When the installer completes, you will be able to administer the 

ddclient

 service as described in the sections below.

Basic settings

All the configuration settings needed to enable Dynamic DNS on your device are available on the Basic settings tab. These are described in the next section.

Service provider

RaspAP makes use of the proven ddclient open source software for Linux to update dynamic DNS entries. The 

ddclient

 software is highly configurable and provides a daemon that updates your external IP at scheduled intervals. Many popular Dynamic DNS services are supported by 

ddclient

 and RaspAP.

Instructions on how to setup your domain for DDNS vary by provider, but the process is generally similar. Begin by selecting a Service provider from the dropdown. RaspAP will assist you by automatically populating the Protocol and Server fields. You may also manually configure the details for your service if so desired.



Note

Some DDNS providers, such as NoIP, distribute their own Linux client to use with their service. It isn't necessary to install this software because the 

ddclient

 daemon already includes this functionality.

Method to obtain IP

There are a variety of different methods to determine your external IP address. A popular one involves a discovery page on the web that resolves your IP. If you choose this method, enter it in the Web address field after selecting this option from the Method to obtain IP select.

Tip

There are many freely available external IP discovery pages you can use. Examples include ChangeIP and this one from Namecheap. Each of these pages perform the same basic function.

Alternatively, you may want to use an IP address from a network interface, your router's firewall status page, or an external command. Each of these options can be specified, thereby giving you a great deal of flexibility.

Login and domain

Enter your DDNS service credentials in the Username and Password fields. Finally, specify the Domain to be updated that will be associated with your device. DDNS providers may also refer to this as a "zone" or "host". These definitions may take several forms, for example:



Check with your DDNS service provider to determine which entry is best for your configuration. To complete your setup, choose Save settings now or proceed with advanced options.

Advanced settings

A subset of advanced options are provided for your configuration. These are not required for the DDNS service to be functional, but may be adjusted to suit your needs.

Enable SSL

You may wish to Enable SSL to ensure that your credentials are not sent over the internet unencrypted. Not all providers support this, however, so this option is disabled by default. Enabling this option for a non-SSL supported provider may result in a connection timeout. Errors such as these have been reported:



For this reason, it's recommended to check with your DDNS service provider before enabling this.

Daemon check interval

Finally, you may define the Daemon check interval to control the length of time between updates performed by 

ddclient

 in the background. This value is specified in milliseconds and defaults to 300.

When you've completed your configuration, choose Save settings and Start Dynamic DNS.

Troubleshooting

Behind the scenes, the 

ddclient

 daemon will determine your external IP using the method you've defined and send this to your DDNS provider. Your provider will then update the IP address corresponding to the DNS "A" (or "address") record for your domain.

If your DDNS provider fails to report your current IP address, or you suspect there might be a problem with the 

ddclient

 configuration on your device, you may generate a detailed debug log.

From the Logging tab, use the Generate log button to invoke the 

ddclient

 daemon and output a troubleshooting log:



This will provide a verbose output of everything 

ddclient

 is doing. If it ends with a 

SUCCESS

 message this indicates that the daemon successfully checked and updated the DNS "A" record with your provider, if neccessary. An example of this is shown below:



If the daemon doesn’t reply with 

SUCCESS

, the debug output should give you some clues as to what the problem is.

Port forwarding

If 

ddclient

 has successfully updated your DDNS provider's "A" record with your IP address, but you are unable to access your device remotely, it's likely your router needs to be configured for port forwarding. This instructs the router to send, or forward, data packets from the external WAN interface to the internal IP address belonging to your device.

You can enable this by using your router's port mapping/forwarding setup. This procedure allows remote computers to connect to a specific device within your internal LAN's private address space. Specifics are highly dependent on the router you have, although the steps are generally straightforward. Consult your router's documentation for details.

Demilitarized zone

An alternative to forwarding specific ports to an internal IP is using a demilitarized zone (DMZ). A home router DMZ is a host on an internal network that has all UDP and TCP ports open and exposed, except those ports otherwise forwarded. By using this method, all the ports (and services) of your device will be directly accessible from the internet, with the attendant security risks that this implies.

This setup is often desirable when a host is running multiple public-facing services that need to be accessed over the internet. In this context, a DMZ provides greater isolation and granular control than is possible with port forwarding. It's also possible to configure different security policies for various DMZ segments. For these reasons, a properly configured DMZ can be a more secure way to expose services to the internet than port forwarding.

The specifics of creating a DMZ are beyond the scope of this document, although at minimum a firewall is strongly advised.

Discussions

Questions or comments about using Dynamic DNS? Join the discussion here.