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Configuring Dynamic DNS in pfSense

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Dynamic DNS (DDNS) is a method of automatically updating a name server in the Domain Name System (DNS), often in real time, with the active DNS configuration of its configured hostnames and/or addresses. The term is used to describe two separate concepts. The first is dynamic DNS updating, which refers to systems that are used to update traditional DNS records without manual editing; this mechanism is described in RFC 2136. The second permits lightweight and immediate updates, often using an update client. These clients provide a persistent addressing method for devices that change their location or IP addresses.

Most internet users who have consumer-grade internet access have a dynamic IP address, most likely assigned by their Internet service provider’s (ISP) DHCP server. These types of IP addresses pose a problem if the user wants to provide a service to other users on the Internet (e.g. a file server). DDNS provides a solution to this problem by providing a means of mapping a potentially rapidly changing IP address to a domain name without suffering the delay which it usually takes for a DNS change to propagate through the hierarchy of DNS servers.

Over the years, several companies and organizations have provided dynamic DNS capabilities. One such company, Dyndns (now called Dyn), provided a free domain name. In 2014, Dyn discontinued their free domain name service. They now charge $40 a year, which I still consider to be a reasonable price. But why pay for domain names when you can still get them for free? Duck DNS provides up to 5 free domain names (all subdomains of duckdns.org; e.g. mydomainname.duckdns.org) and is easy to configure with pfSense. In this article, I will outline the process.

Configuring Dynamic DNS: Creating a Duck DNS Domain Name

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First, create a free account on Duck DNS. Once you have done this, scroll down to the domains section of the page. There will be an edit box for entering your domain name and a green add domain button. Enter a domain and press this button; if your domain isn’t taken already, you should see a page similar to the one shown in the screen capture in which your new domain is listed.

Next you need to install the Duck DNS client on your computer. The Windows version of the client can be downloaded from www.etx.ca and installed easily. The Linux version can be installed even more easily. You will need to install zenity, cron and curl first. Cron comes with most if not all Linux distros; zenity and curl can be installed with the apt-get command. There is a script you can download and execute which provides the same functionality as the Windows Duck DNS client. You will need to enter the domain you created in the first step in the Domain field and in the Token field you need to enter the token generated by Duck DNS for your domain. [This token can be found in the as part of the Update URL provided in the pfSense installation instructions on the Duck DNS website. The token is the part between token= and the ampersand.]

Configuring Dynamic DNS: Adding a DynDns Entry in pfSense

Adding a DynDns entry in pfSense 2.2.4.

With Duck DNS configured and the client installed, now we can log into our pfSense box and configure DynDNS. From the pfSense menu, navigate to Services -> Dynamic DNS. There will be two tabs on the page: DynDns and RFC2136; select DynDns if it is not already selected. Press the plus button to the right of the table to add a new entry. For Service type, select Custom from the dropdown box. The Username and Password fields can be left blank. For the Update URL, you need to copy and paste the URL provided in the pfSense installation instructions on the Duck DNS webside. [You can find this instructions page by clicking on install on the menu at the top and then clicking on pfSense in the Routers section.] For Results Match, enter OK. Once these settings are entered, click on Save to save the changes.

Now the dynamic DNS configuration is complete, but since the whole point of setting up DDNS is to make services on your home network available to others, you are probably going to want to add an entry to the Network Address Translation (NAT) table to redirect incoming traffic to the node providing the service. You also need a corresponding firewall rule to allow the traffic through (NAT can create such a rule automatically). This is assuming that you didn’t already alter the NAT/firewall rules for the service you want to make available. One potential issue is that your ISP may block port 80 traffic, so if you want to set up your own web server, you may have to use a different port. [You can use NAT to redirect traffic from the port you selected to port 80.] If you cannot access the service you are trying to make available from the WAN side, you might want to try a different port and see if it works.

Source: pfsensesetup.com (great website for all things related to PfSense)

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