Dynamic DNS, or DynDNS for short, is a domain name service which allows static Internet domain names to be assigned to a computer with a varying IPClosed address. You can sign up for the DynDNS service at the website of the respective DynDNS service provider to get a DNSClosed alias that will automatically be updated when your uplink IP address changes. Once you have registered to this service, you will receive a hostname, username, and password, which are necessary for the configuration.

To configure DynDNS, proceed as follows:

  1. On the DynDNS tab, click New DynDNS.

    The Add DynDNS dialog box opens.

  2. Make the following settings:

    Type: The following DynDNS services are available:

    Note – In the Server field the URL is displayed to which Sophos UTM sends the IP changes.

    Assign (not with type FreeDNS): Define the IP address the DynDNS name is to be associated with. Selecting IP of Local Interface is useful when the interface in question has a public IP address. Typically, you will use this option for your DSL uplink. When you select First public IP on the default route no interface needs to be specified. Instead, your Sophos UTM will send a WWW request to a public DynDNS server which in return will respond with the public IP you are currently using. This is useful when your Sophos UTM does not have a public IP address but is located inside a private network, connected to the Internet via a masquerading router.

    Note – FreeDNS always uses the first public IP address on the default route.

    Interface (only with IP of local interface): Select the interface for which you want to use the DynDNS service, most likely this will be your external interface connected to the Internet.

    Record (only with Dyn and FreeDNS): Select the record you want to use for the DynDNS service. Decide between A (IPv4), A & AAAA (dual stack) (only with Dyn) and AAAA (IPv6) (only with FreeDNS).

    Hostname (not with type Open DNS IP update): Enter the domain name you received from your DynDNS service provider (e.g., example.dyndns.org). Note that you need not adhere to a particular syntax for the hostname to be entered here. What you must enter here exclusively depends on what your DynDNS service provider requires. Apart from that, you can also use your DynDNS hostname as the gateway's main hostname, which, however, is not mandatory.

    Label (only with type Open DNS IP update): Enter the label given to the network. Please refer to the OpenDNS Knowledge Base for further information.

    Aliases (optional, only with some types): Use this box to enter additional hostnames which should point to the same IP address as the main hostname above (e.g., mail.example.com, example.com).

    MX (optional, only with type DNS Park, DynDNS, or easyDNS): Mail exchangers are used for directing mail to specific servers other than the one a hostname points to. MX records serve a specific purpose: they let you specify the host (server) to which mail for a specific domain should be sent. For example, if you enter mail.example.com as Mail Exchanger, mail addressed to user@example.com would be delivered to the host mail.example.com.

    MX priority (optional, only with type DNS Park): Enter a positive integer number indicating whether the specified mail server should be preferred for delivery of mail to the domain. Servers with lower numbers are preferred over servers with higher numbers. You can usually leave the field blank because DNS Park uses a default value of 5 which is appropriate for almost all purposes. For technical details about mail exchanger priorities, see RFC 5321.

    Backup MX (optional, only with type DynDNS or easyDNS): Select this checkbox only if the hostname named in the Hostname text box is to serve as main mail exchanger. Then the hostname from the MX text box will only be advertised as a backup mail exchanger.

    Wildcard (optional, only with type DynDNS or easyDNS): Select this option if you want subdomains to point to the same IP address as your registered domain. Using this option an asterisk (*) will be added to your domain serving as a wildcard (e.g., *.example.dyndns.org), thus making sure that, for example, www.example.dyndns.org will point to the same address as example.dyndns.org.

    Username: Enter the username you received from the DynDNS service provider.

    Password: Enter the password you received from the DynDNS service provider.

    Comment (optional): Add a description or other information.

  3. Click Save.

    The new DynDNS appears on the DynDNS list. The service is still disabled (toggle switch is gray).

  4. Enable DynDNS.

    Click the toggle switch to enable the DynDNS service.

    The service is now enabled (toggle switch is green).

To either edit or delete a DynDNS, click the corresponding buttons.

You can use multiple DynDNS objects at the same time. When all settings for two hostnames are identical, it is recommended to use the Aliases option—instead of creating two distinct objects.