Dual-Stack Lite (DS-Lite) is a technology that allows applications that use the Internet Protocol v4 (IPv4) to access the internet via Internet Protocol v6 (IPv6). DS-Lite is used by internet providers that do not have sufficient public IPv4 addresses for their customers and therefore set up IPv6 internet connections with DS-Lite for them.

When used on DS-Lite internet connections, the FRITZ!Box encapsulates all data from IPv4 applications into IPv6 packets and then transmits them to the internet service provider via the IPv6 connection (IPv6-in-IPv4 tunnels). There, a special server unpacks the IPv6 packets and forwards the IPv4 data they contain to the actual destination on the internet.

With DS-Lite, almost all IPv4 applications can be used without restriction. It is only not possible to access the FRITZ!Box or devices in the home network over the internet via IPv4 because the FRITZ!Box does not obtain a public IPv4 address from the internet service provider. This means that if you are operating servers in the home network, they cannot be accessed from the internet via IPv4.

The Port Control Protocol (PCP) can be used to resolve this type of connection problem. With PCP, the FRITZ!Box can set up port sharings for itself at the internet service provider's, making it unnecessary to have the missing public IPv4 address. The FRITZ!Box already supports PCP and the first providers of DS-Lite internet connections could start to support PCP in the course of the year.

Note:If the FRITZ!Box is being used on a DS-Lite internet connection, you can access it and the home network from the internet over IPv6. However, this type of IPv6 connection can only be established if both parties have an IPv6 internet connection, which is not the case in all mobile networks and Wi-Fi hotspots, for example.