IS-IS History

https://en.wikipedia.org/wiki/IS-IS
https://en.wikipedia.org/wiki/OSI_protocols
https://en.wikipedia.org/wiki/Type-length-value

  • Created for the OSI Protocol Suite
  • Integrated IS-IS: the mutation.
  • IS-IS dictionary:
    • IS = Intermediate System  (Routers)
    • ES = End System
    • TLV = Type Length Value
    • NSAP = Network Service Access Point
      • (OSI protocols equivilent of the TCP/IP’s IP Address)
  • IS-IS features:
    • Link State Routing Protocol  (Same as OSPF)
    • NSAP address assigned per router
    • Dijkstra SPF powered (Same as OSPF)
      • PRC efficient
    • Hellos Establisch neighbors at Layer 2 ( source MAC, Multicast Mac )
    • Two routing levels ( Level 1 and Level 2 )
    • Area Based Design ( Routers know their area )
    • default link cost = 10

IS-IS High level Design

  • Two routing databases
    • Level1 and Level2
      • Level 1 routers find closest Level2 Exit.
    • Area defined by
    • 49.0001  ( Area 1 )
      • 49 private adressing , 0001 is area 1
  • Three router types

IS-IS Neighbors and Area Design

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