In the FRITZ!Box, you can configure native IPv4 and IPv6 internet connections or an IPv6 connection over a tunnel protocol. Various settings are available:

Using a native IPv4 connection

If the setting "Use native IPv4 connection" is selected, the FRITZ!Box establishes IPv4 and IPv6 internet connections:

• The FRITZ!Box establishes a native IPv4 connection first.
• If the internet service provider announces the IPv4 address of a 6RD gateway to the FRITZ!Box via DHCPv4, the FRITZ!Box also establishes a 6RD tunnel for IPv6 in addition to the IPv4 connection.
• If the internet service provider does not announce a 6RD gateway to the FRITZ!Box, the FRITZ!Box also tries to establish a native IPv6 connection using Dual-Stack in addition to the IPv4 connection.
• If neither a 6RD tunnel nor a native IPv6 connection is established, then the FRITZ!Box will not establish an IPv6 connection.

The setting "Use native IPv4 connection" makes sense if if the internet connection supports IPv4 and it is not known which IPv6 settings the internet service provider expects.

Using a native IPv6 connection

If the setting "Use native IPv6 connection" is selected, the FRITZ!Box establishes a native IPv6 internet connection and also attempts to establish an IPv4 connection using DS-Lite:

• The FRITZ!Box establishes a native IPv6 connection first.
• If the internet service provider announces an AFTR address to the FRITZ!Box via DHCPv6 or the setting "Establish IPv4 connection via DS-Lite" is enabled and an AFTR was entered manually, the FRITZ!Box also establishes an IPv4 connection using DS-Lite in addition to the IPv6 connection.
• If the internet service provider does not announce an AFTR address to the FRITZ!Box and the native IPv6 connection cannot be established, the FRITZ!Box establishes a native IPv4 connection.

The setting "Use native IPv6 connection" makes sense if the internet connection supports a native IPv6 connection and IPv4 using DS-Lite.

Using only IPv6

If the setting "Use only IPv6" is selected, the FRITZ!Box only establishes a native IPv6 internet connection. The FRITZ!Box does not establish an IPv4 connection.

The setting "Use only IPv6" makes sense if you have a pure IPv6 internet connection and the internet service provider makes suitable translation procedures for IPv4 destinations available (for example NAT64 / DNS64 or 464XLAT).

Using IPv6 with a tunnel protocol

If the setting "Use IPv6 with a tunnel protocol" is selected, the FRITZ!Box establishes a native IPv4 internet connection and also establishes a tunnel for IPv6. When using a tunnel protocol, the FRITZ!Box packs IPv6 packets into IPv4 packets and sends them via the IPv4 internet connection to a special gateway that unpacks the packets again and forwards the IPv6 data they contain to the IPv6 area of the internet.

The FRITZ!Box supports various tunnel protocols:

• 6to4: 6to4 is a tunnel protocol that can be used with all IPv4 internet connections. It is not necessary to register with a service provider. The IPv4 address of the FRITZ!Box is rendered on an IPv6 address space according to a prescribed mechanism. This means that every change to the IPv4 address also changes the IPv6 address space of the FRITZ!Box.
• 6RD: The 6RD tunnel protocol is based on the tunnel protocol 6to4, but it can only be used if the IPv4 internet service provider offers a 6RD gateway. Unlike with 6to4, the same gateway is always used with 6RD.

• 6in4: The 6in4 tunnel protocol can only be used if the IPv4 internet service provider offers a 6in4 gateway. Unlike with 6RD, the gateway must always be set up manually with 6in4.

The setting "Use IPv6 with a tunnel protocol" makes sense if the internet service provider does not support IPv6 on the connection.