What is Integrated ISIS?

The IS-IS Routing Protocol may be used as an IGP to support IP as well as OSI. This allows a single routing protocol to be used to support pure IP environments, pure OSI environments, and dual environments. Integrated IS-IS is deployed extensively in an IP-only environment in the top-tier Internet service provider (ISP) networks. The IS-IS working group of the Internet Engineering Task Force (IETF) developed the specification for Integrated IS-IS (RFC 1195).