Is-Is Overview; Basic Concepts - 3Com MSR 50 Series Configuration Manual

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IS-IS Overview

Basic Concepts

IS-IS C
ONFIGURATION
When configuring IS-IS, go to these sections for information you are interested in:
"IS-IS Overview" on page 877
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"IS-IS Configuration Task List" on page 892
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"Configuring IS-IS Basic Functions" on page 893
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"Configuring IS-IS Routing Information Control" on page 894
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"Tuning and Optimizing IS-IS Network" on page 898
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"Configuring IS-IS GR" on page 904
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"Displaying and Maintaining IS-IS Configuration" on page 905
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"IS-IS Configuration Example" on page 906
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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.
IS-IS terminology
Intermediate system (IS). An IS, similar to a router in TCP/IP, is the basic unit in
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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
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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
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same routing protocol in a routing domain.
Area. An area is a division unit in a routing domain. The IS-IS protocol allows a
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routing domain to be divided into multiple areas.
Link State Database (LSDB). All link states in the network forms the LSDB. There
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is at least one LSDB in each IS. The IS uses SPF algorithm and LSDB to generate
its own routes.