Cisco® CCNA Exam Cram Notes : Routing Protocol Types

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3. Routing Technologies

2. Routing protocol types

There are broadly three types of routing protocols:

1. Distance Vector (Number of hops) : Distance vector routing determines the direction (vector) and distance to any link in the internetwork. Typically, the smaller the metric, the better the path. Examples of distance vector protocols are RIP and IGRP.

Distance vector routing is useful for smaller networks. The limitation is that any route which is greater than 15 hops is considered unreachable. One important thing that differentiates distance vector with Link state is that distance vector listens to second hand information to learn routing tables whereas, Link state builds its routing tables from first hand information. Distance vector algorithms call for each router to send its entire routing table to each of its adjacent neighbors.

2. Link State Routing : Link State algorithms are also known as Shortest Path First (SPF) algorithms. SPF recreates the exact topology of the entire network for route computation by listening at the first hand information.

Link State takes bandwidth into account using a cost metric. Link State protocols only send updates when a change occurs, which makes them more attractive for larger networks. Bandwidth and delay are the most heavily weighed parts of the metric when using Link-State protocols. EX: OSPF and NLSP.

Benefits of Link State protocols:

  • Allows for a larger scalable network
  • Reduces convergence time
  • Allows "supernetting"

3. Balanced Hybrid : Balanced Hybrid combines some aspects of Link State and Distance Vector routing protocols. Balanced Hybrid uses distance vectors with more accurate metrics to determine the best paths to destination networks. EX: EIGRP.

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