Hierarchical Routing

• aggregate routers into regions, “autonomous systems” (AS)

• routers in same AS run same routing protocol

  • “intra-AS” routing protocol
  • routers in different AS can run different intra-AS routing protocol

• special routers in AS

• run intra-AS routing protocol with all other routers in AS

• also responsible for routing to destinations outside AS

  • run inter-AS routing protocol with other gateway routers

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