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Intermediate System to Intermediate System

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Also known as IS-IS

Intermediate System to Intermediate System (IS-IS, also written ISIS) is a link-state interior gateway protocol (IGP) used to exchange routing information within a network. Routers share network topology information so they can find the most efficient paths for data. IS-IS is typically deployed within a single autonomous system and is used in large enterprise and service provider networks.

~17 min read

Encyclopedic overview

19 sections
Contents
  • Description
  • History
  • IS-IS terminology
  • Packet types
  • IS-IS addressing and NET
  • Hostname resolution
  • Areas and levels
  • Attribute bits in LSPs
  • Wide metrics
  • Adjacency formation
  • Broadcast segments and designated intermediate system
  • Authentication
  • IPv6 support and multi-topology
  • IS-IS path selection
  • BFD support
  • Other uses
  • Related protocols
  • References
  • External links

Intermediate System to Intermediate System (IS-IS, also written ISIS) is a link-state interior gateway protocol (IGP) used to exchange routing information within a network. Routers share network topology information so they can find the most efficient paths for data. IS-IS is typically deployed within a single autonomous system and is used in large enterprise and service provider networks.

The IS-IS protocol is defined in ISO/IEC 10589:2002 as an international standard within the Open Systems Interconnection (OSI) reference design.

Excerpted from Wikipedia’s “Intermediate System to Intermediate System” article, available under the CC BY-SA 4.0 licence.