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IS-IS CONFIGURATION
When configuring IS-IS, go to these sections for information you are interested in:
■ “IS-IS Overview” on page 325
■ “IS-IS Configuration Task List” on page 340
■ “Configuring IS-IS Basic Functions” on page 341
■ “Configuring IS-IS Routing Information Control” on page 342
■ “Tuning and Optimizing IS-IS Network” on page 346
■ “Configuring IS-IS GR” on page 352
■ “Displaying and Maintaining IS-IS” on page 353
■ “IS-IS Configuration Example” on page 354
n
The term “router” in this document refers to a router in a generic sense or an
Ethernet switch running routing protocols.
IS-IS Overview Intermediate System-to-Intermediate System (IS-IS) is a dynamic routing protocol
designed by the International Organization for Standardization (ISO) to operate on
the connectionless network protocol (CLNP).
The IS-IS routing protocol has been modified and extended in RFC 1195 by the
International Engineer Task Force (IETF) for application in both TCP/IP and OSI
reference models, and the new one is called Integrated IS-IS or Dual IS-IS.
IS-IS is an interior gateway protocol (IGP) used within an Autonomous System. It
adopts the Shortest Path First (SPF) algorithm for route calculation.
Basic Concepts IS-IS terminology
■ Intermediate system (IS). An IS, similar to a router in TCP/IP, is the basic unit in
IS-IS protocol to generate and propagate routing information. In the following
text, an IS is a router.
■ End system (ES). An ES refers to a host system in TCP/IP. ISO defines the ES-IS
protocol for communication between an ES and an IS, therefore an ES does not
participate in the IS-IS process.
■ Routing domain (RD). A group of ISs exchange routing information with the
same routing protocol in a routing domain.
■ Area. An area is a division unit in a routing domain. The IS-IS protocol allows a
routing domain to be divided into multiple areas.
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