Sun RBridges provide the ability to have an entire campus, with multiple physical links, look to IP like a single subnet. The design allows for zero configuration of switches within a campus, optimal pair-wise routing, safe forwarding even during periods of temporary loops, and the ability to cut down on ARP/ND traffic. The design also supports VLANs, and allows forwarding tables to be based on RBridge destinations (rather than endnode destinations), which allows internal routing tables to be substantially smaller than in conventional bridge systems. This document is a work in progress; we invite you to participate on the mailing list at http://www.postel.org/RBridge