Dynamic DNS Configuration in pfSense

Dynamic DNS Explained

Dyanmic 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, addresses or other information. The term is used in two different ways. At the administrative levels of the Internet, “dynamic DNS updating” refers to systems that are used to update traditional DNS records without manual editing. But another type of dynamic DNS permits lightweight and immediate updates to its local database, often using a web-based mechanism. It is used to resolve a domain name to an IP address that may change frequently, thus providing a persistent addressing method for devices that change their location or configuration.

It is the latter type of DDNS in which we are interested. End users of Internet access receive an allocation of IP addresses, often only a single address, by their service providers. If you are a residential or small business customer, you will probably have an IP address assigned dynamically. Such dynamic IP addresses present a problem if the customer wants to provide a service to other users, such as a website. As the IP address may change frequently, corresponding domain names must be quickly re-mapped in the DNS servers to maintain accessibility using a well-known domain name. To this end, many providers offer commercial or free DDNS service for this scenario, with reconfiguration generally implemented in the user’s router or computer.

Dynamic DNS providers offer a software client program that automates the discovery and registration of the client system’s public IP addresses. The client program connects to the DDNS provider from the client’s private network and links the public IP address of the home network with a hostname. Depending on the provider, the hostname is registered with a domain owned by the provider or the customer’s own domain name. These services can function by a number of mechanisms. Often the use an HTTP service request. The provider might use RFC 2136 to update the DNS servers (more on RFC 2136 later). Many home networking modem/routers have clients for several DDNS providers built into their firmware, and pfSense is no exception, making it very easy to use DDNS with pfSense.

Configuring Dynamic DNS in pfSense

Dynamic DNS

Configuring the DDNS client in pfSense 2.0.

To enable DDNS in pfSense, first navigate to Services -> Dynamic DNS. If the “DynDNS” tab is not selected already, click on it. Press the “plus” button on the right side of the page to add a new DDNS client. At “Service type“, select a DDNS service provider from the dropdown box. At “Interface to monitor“, specify an interface (typically the WAN). At “Hostname“, specify the hostname (either one supplied by the provider or your own hostname) that you wish to associate with your network’s public IP. At “MX“, set your MX record if you need one (thus allowing you to configure your subdomain for email routing) and if your service supports it. At “Wildcards“, enable wildcards if desired. This is useful if the domain name specified is not a fully qualified domain name (FQDN); for example, if your DDNS address is myplace.dyndns.org and you enable wildcards, then x.myplace.dyndns.org will work as well (x is the wildcard). At “Username” and “Password“, specify your username (username is required for all types except Namecheap and FreeDNS) and password. At “Description“, enter an appropriate description. Then press the “Save” button to save the settings and, on the next page, press “Apply Changes” to apply the changes if necessary.

Dynamic DNS

If our DDNS service provider is not one of the pre-configured ones, we can still use pfSense to act as a client for the provider if it complies with RFC 2136.

To make sure everything is working go back to Services -> Dynamic DNS. If the cached IP is green then the hostname was successfully updated. It is also probably a good idea to ping the domain to make sure the domain name resolves to the correct IP address. Even with DDNS, it can take several minutes for the changes to propagate to other DNS servers. The client will automatically update the dynamic host each time the WAN IP changes or every 25 days. You probably want to make sure your client is connecting to the service, since some providers will remove inactive hosts if they have not been updated for 30 days.

This configuration will work in most cases; however, it is possible you may be using a DDNS service provider that is not on the list at “Service type“. If this is the case, you can still use pfSense to to connect to your DDNS provider as long as the provider adheres to the RFC 2136 standard. To enable this, navigate to Services -> Dynamic DNS as before, but select the RFC 2136 tab. Press the “plus” button to add a new entry. Specify the “Interface to monitor” and “Hostname” as outlined in the instructions for the “DynDNS” tab. You can also specify a time to live for data from our client at “TTL“. You must also specify a “Key Name” that matches the key name setting on the DNS server, a “Key type” (zone, host, or user), and an HMAC-MD5 “Key“. You must specify the server address at “Server“. Check the check box at “Protocol” if the DDNS provider uses TCP instead of UDP. At “Description“, enter an appropriate description. Then press the “Save” button to save the changes and “Apply changes” to apply changes if necessary.

External Links:

Dynamic DNS on Wikipedia

Dynamic DNS on doc.pfsense.org

RFC 2136 Dynamic DNS on doc.pfsense.org

How to Configure Dynamic DNS in pfSense at HubPages

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