Chapter 4. IS-IS

Intermediate System-to-Intermediate System (IS-IS) is a link state routing protocol that is part of the OSI family of protocols. Like OSPF, it uses Dijkstra’s SPF algorithm to choose routes. IS-IS is a classless interior gateway protocol that uses router resources efficiently and scales to large networks, such as large Internet service providers (ISP).

Table 4-1 lists some IS-IS terms, acronyms, and their meanings.

Table 4-1. IS-IS Acronyms

Term

Acronym

Description

Circuit ID

Identifies a physical interface on the router.

Complete Sequence Number PDU

CSNP

A summary of a router’s complete LSDB.

Connectionless Network Protocol

CLNP

OSI protocol used to provide the connectionless services.

Connectionless Network Services

CNLS

OSI data delivery service ...

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