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Routing Protocols

Routing Protocols. Brandon Wagner. Learning Outcomes. Understand Interior and External Routing protocols and their differences Understand Distance-Vector and Link-State routing methods Describe the routing mechanisms of common routing protocols. What does a Routing Protocol do?.

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Routing Protocols

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  1. Routing Protocols Brandon Wagner

  2. Learning Outcomes • Understand Interior and External Routing protocols and their differences • Understand Distance-Vector and Link-State routing methods • Describe the routing mechanisms of common routing protocols.

  3. What does a Routing Protocol do? • Determine the best forwarding path from point A to point B. • Prevent routing loops. • Builds a routing table. • Destination and gateway

  4. Two Types • Interior Gateway Protocol • Routing within an Autonomous System (AS) • Exterior Gateway Protocol • Routing between Autonomous System’s. • Autonomous System • Group of IP networks controlled by a single common administrator. • Managed by IANA (Internet Assigned Numbers Authority) • BYU has 1 assigned AS number.

  5. IGP: Interior Gateway Protocols • Distance-Vector Routing Protocol • Distance – the cost of reaching the destination. • Vector – direction (which interface) to forward traffic. • Information is only exchanged with neighbors. • Examples • RIP – Routing Information Protocol • EIGRP – Enhanced Interior Gateway Routing Protocol • Link-State Routing Protocol • Link – the speed of the link (10 Meg / 100 Meg / 1 Gb / 10 Gb) • State – Is the interface up or down? • The whole network topology is known by every router • Examples • OSPF – Open Shortest Path First • IS-IS – Intermediate System to Intermediate System

  6. Other Examples

  7. Distance-Vector: RIP • Mechanism: Each router sends routing table to neighbor. Neighbor then forwards routing table to it’s neighbor. • Algorithm: Bellman-Ford • First Deployed: 1967 • Cost: Hop Count • Maximum # of hops is 15. • Best Fit: Small networks with minimal changes.

  8. Distance-Vector: EIGRP • Mechanism: • Neighbor Table – List of all directly connected neighbors • Topology Table – all available destination routes from neighbors • Route Table – built from applying metric formula to Topology Table • First Deployed: 1995 • Cost: Delay, Bandwidth, Reliability, Load • Best Fit: Enterprise Architecture Model • Packet Types: Update, Query, Reply, Hello • Sometimes called Hybrid – why?

  9. Link-State: OSPF • Mechanism: • Link State Advertisements (LSA) sent out to all other routers. • Each router builds a LSDB • The Database is converted into a weight graph. • Each router determines shortest path to each other. • Algorithm: Dijkstra’s • Cost: Definable – bandwidth is commonly used. • Best Fit: Very, very, VERY large networks. • Split into network areas to reduce the size of update packets.

  10. Distance-Vector vs Link-State • Distance Vector • Pro’s • Only have receive updates from neighbors. • Simple to use and smaller overhead. • Con’s • Updates are spread node-by-node. • Count-to-infinity problem. • Link State • Pro’s • Each router has a full network topology. • Convergence after a topology change is quicker. • Con’s • Requires more processing power and memory.

  11. EGP: Exterior Gateway Protocol • BGP – Border Gateway Protocol • Routes the internet • The full route table is currently 357,000 path entries • Path-Vector Routing Algorithm • Tracks paths according to AS. • Local preference determine best path to destination network. (Border Example) • Does NOT track routes through individual routers.

  12. Routing Reviewed Questions?

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