Chapter 4. IS-IS Theory and Operation

Intermediate System-to-Intermediate System (IS-IS) Protocol is widely used in Europe, in public utility companies, and in global service provider networks. IS-IS was originally developed to provide routing for the ISO protocol stack, including the most commonly recognized transport protocol within that stack, Connectionless Network Service (CLNS). IS-IS was adapted to use for IP routing by the Internet Engineering Task Force (IETF), which has since added IPv6 routing and, most recently, Layer 2 routing capabilities to the protocol.

In IS-IS, a router is called an intermediate system (IS). Both terms are used throughout this document.

Neighbor Relationships

IS-IS forms neighbor relationships for two primary ...

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