This draft describes a mechanism that allows a single router to share one or more circuits among multiple Intermediate System To Intermediate System (IS-IS) routing protocol instances. Multiple instances allow the isolation of resources associated with each instance. Routers will form instance specific adjacencies. Each instance can support multiple topologies. Each topology has a unique Link State Database (LSDB). Each Protocol Data Unit (PDU) will contain a new Type Length Value (TLV) identifying the instance and the topology(ies) to which the PDU belongs. This draft obsoletes RFC 6822 if approved.