IGP and EGP

AS (Autonomous System)
  • Autonomous
    • Existing as an independent entity
  • Group of IP routes under common control
  • RFC 1930, Section 3: Definitions
    • "An AS is a connected group of one or more IP prefixes run by one ore more network operators which has a SINGLE and CLEARLY DEFINED routing policy."
  • Important point of reference for discussing Interior Gateway Protocols and Exterior Gateway Protocols
IGP (Interior Gateway Protocol)
  • Used within a single autonomous system (AS)
    • Not intended to route between AS
    • That's why there's Exterior Gateway Protocols (EGPs)
  • IPv4 dynamic routing
    • OSPFv2 (Open Shortest Path First)
    • RIPv2 (Routing information Protocol version 2)
    • EIGRP (Enhanced Interior Gateway Routing Protocol)
  • IPv6 dynamic routing
    • OSPFv3
    • EIGRP for IPv6
    • RIPng (RIP next generation)
EGP (Exterior Gateway Protocol)
  • Used to route between autonomous systems
    • Leverages the IGP at the AS to handle local routing
  • BGP (Border Gateway Protocol)
    • Many organizations use BGP as their EGP

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