University of Warsaw By and large, a correct operation of a RPL network requires border routers to be up. In many applications, it is beneficial for the nodes to detect a crash of a border router as soon as possible to trigger fallback actions. This document describes RNFD, an extension to RPL that expedites border router failure detection, even by an order of magnitude, by having nodes collaboratively monitor the status of a given border router. The extension introduces an additional state at each node, a new type of RPL Control Message Options for synchronizing this state among different nodes, and the coordination algorithm itself.