IPv6 host auto-configuration has been part of IPv6 specification from the start, but IPv6 routers still require manual configuration and administration. This is not only unacceptable for emerging home and SOHO networks, but it also complicates network management for complex corporate networks. To enable easy and ubiquitous deployment of future IPv6 networks, there is a need for an IPv6 router auto-configuration protocol to complement IPv6 host auto-configuration to make IPv6 networks truly plug-and-play. In this paper we address this issue and propose an IPv6 router auto-configuration algorithm. The idea is for each router to assign unique subnetids to each of their interfaces during startup, and cooperate with other routers in the network to maintain the uniqueness of their subnetid assignment in the face of topological changes. We show how the proposed algorithm can be implemented by a simple modification of the basic intra-domain topology broadcast algorithm. Finally we extend the algorithm to hybrid networks, where some of the segments are manually configured by the administrators and the rest of the segments are auto-configured by the routers. © Springer-Verlag Berlin Heidelberg 2006.