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Knowledge document #30

Setting up dynamic DNS in the FRITZ!Box

With dynamic DNS you can access your FRITZ!Box as well as applications and services in the home network for which you configured port sharing in the FRITZ!Box over the internet at a fixed domain name. This way you can easily access a NAS system or perform remote maintenance on a computer with Microsoft Remote Desktop, for example, even if the FRITZ!Box's public IP address changes at regular intervals.

Note:You can also use the free AVM service MyFRITZ! to easily and securely access your FRITZ!Box and home network over the internet at any time.

Requirements / Restrictions

  • The FRITZ!Box must establish its own connection to the internet through a modem (for example a DSL or cable modem).
  • For IPv4 internet access, the FRITZ!Box must obtain a public IPv4 address from the internet service provider.
  • For IPv6 internet access, the FRITZ!Box must obtain an IPv6 address from the internet service provider.

Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.

1 Setting up dynamic DNS

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Permit Access" in the "Internet" menu.
  3. Click on the "DynDNS" tab.
  4. Enable the option "Use DynDNS".
  5. Select your dynamic DNS provider from the drop-down list and enter the login information you received from your provider in the corresponding fields. If your dynamic DNS provider is not displayed:
    1. Select the entry "User-defined".
    2. Enter your login information and the update URL. You can create the update URL yourself as described in the section "Creating your own update URL".
  6. Click "Apply" to save the settings.
  7. Now the FRITZ!Box transmits its current IP addresses to the provider every time it connects to the internet so that the FRITZ!Box can always be contacted via its unique dynamic DNS domain name.

2 Creating your own update URL

If your dynamic DNS provider is not listed in the FRITZ!Box, check your provider's website for the update URL and replace the placeholder names in your provider's update URL with the placeholder names supported by the FRITZ!Box.

Information in the update URL

The information contained in the update URL are required to update the IP address. Different dynamic DNS providers use not only different information, but even different names for this information.

One item of information every dynamic DNS provider uses in the update URL is the domain for which the IP address is to be updated. The entry for the domain can appear in the update URL under the following names: domain, domainname, host, hostname. Other designations are also possible. What matters is that you use the name prescribed by your provider.

All information in the update URL is assigned a value. The "domain" information is assigned the value of the name of the domain to be updated. A placeholder is entered in the update URL for the domain name. Placeholders are used for other information as well. The names of the placeholders are prescribed by the FRITZ!Box. When the FRITZ!Box executes the update request, for instance, after the IP address changes, then the placeholders are replaced by the current values.

The following table shows which entries that can be contained in an update request. Different providers may call these entries by different names. The placeholder used in the FRITZ!Box for each entry is listed. It is essential that these placeholders be used in the update URL exactly as they appear in the table:

EntryPlaceholder in the update URL of the FRITZ!Box
Username <username>
Password <pass> or <passwd>
Domain name <domain>
IPv4 address <ipaddr>
IPv6 address <ip6addr>
Dual-stack <dualstack>
LAN prefix <ip6lanprefix>
  • The pointed brackets are part of the placeholder and absolutely must be entered in the update URL.
  • If your provider uses other placeholder names, these must be replaced by the placeholder names from the above table.
  • Some providers expect some of the data to be transmitted in Base64-coded format. All data that must be encoded for transmission must be designated as follows in the update URL of the FRITZ!Box:
    <b64>the data to be encoded is contained here</b64>

Schema of the Update URL

The update URL is always structured according to the same schema: The update instruction is followed by the list of parameters. A parameter is a datum along with the assigned value. The call for the update instruction is followed by a question mark and then the list of parameters. Every update URL in the list of update URLs complies with this schema.

Example for the update URL for the IPv4 address for the provider dyn.com:
members.dyndns.org/nic/update?system=dyndns&hostname=<domain>&myip=<ipaddr>&wildcard=NOCHG
The update instruction is: "members.dyndns.org/nic/update".
After the update instruction comes the "?".
The "?" is followed by the list of parameters:
"system=dyndns&hostname=<domain>&myip=<ipaddr>&wildcard=NOCHG".

Structure of the parameter list

The parameter list is a sequence of all parameters which the dynamic DNS provider expects in the update URL. A parameter consist of a datum and the value assigned to it. The value is assigned using an equal sign. The individual parameters are separated from each other by an &.

Example for the update URL of the IPv4 address for the provider dyn.com with 4 parameters:
members.dyndns.org/nic/update?system=dyndns&hostname=<domain>&myip=<ipaddr>&wildcard=NOCHG
system=dyndns
hostname=<hostname>
myip=<ipaddr>
wildcard=NOCHG



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