tunnelbroker

A tunnelbroker is a service that provides a tunnel between an IPv6 network and the IPv4 Internet, enabling devices on an IPv4-only network to communicate using IPv6. The broker typically allocates a routable IPv6 prefix to the customer and offers an IPv4 endpoint to which the customer’s router or host attaches an IPv6-in-IPv4 tunnel, often using the 6in4 mechanism. The tunnel carries encapsulated IPv6 packets over the IPv4 network to the broker’s IPv4 address, which then routes them toward the IPv6 Internet.

In practice, a user configures a tunnel client or router to establish a tunnel to the broker’s IPv4 address, receives the provided IPv6 prefix (for example a /64 or /48), and advertises an IPv6 gateway to internal devices. The customer’s devices can then use native IPv6 addresses within the assigned prefix, while the underlying transport remains IPv4.

Historically, tunnel brokers played a key role during early IPv6 adoption when native IPv6 connectivity was limited. Notable providers have included Hurricane Electric’s tunnelbroker.net and SixXS. SixXS operated a popular service for 6in4 and related tunneling but discontinued operations around 2017–2018; Hurricane Electric continues to operate a widely used broker. Today, native IPv6 deployment and dual-stack configurations reduce reliance on tunnel brokers, though they remain useful for testing, education, or temporary access.