Routing - Interior Gateway Protocols

  • Basics of Routing

    • Routing involves updating routing tables with the most efficient paths to destination networks.
    • Routing protocols enable routers to communicate and share information about network paths.

  • Routing Protocols Overview

    • Two Main Categories:
    • Interior Gateway Protocols (IGPs)
    • Exterior Gateway Protocols (EGPs)

  • Interior Gateway Protocols (IGPs):

    • Used for sharing information within a single autonomous system (AS).
    • Definition of Autonomous System:
    • A collection of networks under a single operator (e.g., large corporations or ISPs).
    • Examples of IGPs:
    • Link State Routing Protocols
    • Distance Vector Protocols

  • Distance Vector Protocols:

    • An older protocol standard.
    • Routers share simple distance metrics (hops) to known networks with their neighbors.
    • Mechanism:
    • Each router maintains a routing table with network destinations and the number of hops to each.
    • Each router sends this table to directly connected routers (neighbors).
    • Illustration:
    • Router A has a route to Network X (10.1.1.0/24) through Router C (4 hops).
    • Router B informs Router A that Network X is reachable in just 2 hops.
    • Router A updates its table to send traffic to Router B instead (3 hops total).
    • Limitations:
    • Lacks awareness of the overall state of the network, may react slowly to distant changes.

  • Link State Protocols:

    • More advanced protocol offering a comprehensive approach.
    • How They Work:
    • Each router advertises the state of its interfaces, sharing detailed connection information.
    • All routers gain visibility of the complete topological structure of the network.
    • Routers run algorithms to determine the best paths based on complete data.
    • Requirements:
    • Increased memory to store network details.
    • Greater processing power to compute optimal routes.
    • Current Trend:
    • As hardware improves, link state protocols are becoming more common, rendering distance vector protocols less practical.