Ospf basics

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Overview

  • OSPF is an interior gateway protocol

Structure

  • encapsulates its data directly in IP
  • protocol number 89
  • multicast addresses 224.0.0.5
  • variety authentication methods

Router relationships

  • router identifies with Hello packet
  • link state protocol
  • neighbor relationships

Adjacency state machine

  • down
  • attempt
  • init
  • 2-way
  • exstart
  • exchange
  • loading
  • full

Protocol messages

  • Hello
  • Database Description
  • Link State Request
  • Link State Update
  • Link State Acknowledgment

OSPF Version 3

OSPF Header Version 3
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Version
Type
Length
Router ID
Area ID
Checksum
Instance ID
Reserved
Data