6.3 Routing Protocols Overview  
  6.3.3 Routing protocols  
At the Internet layer of the TCP/IP suite of protocols, a router can use an IP routing protocol to accomplish routing through the implementation of a specific routing algorithm. Examples of IP routing protocols include:
  • RIP – A distance vector interior routing protocol
  • IGRP – Cisco's distance vector interior routing protocol
  • OSPF – A link-state interior routing protocol
  • EIGRP – Cisco’s advanced distance vector interior routing protocol
  • BGP – A distance vector exterior routing protocol

Routing Information Protocol (RIP) was originally specified in RFC 1058. Its key characteristics include the following:

  • It is a distance vector routing protocol.
  • Hop count is used as the metric for path selection.
  • If the hop count is greater than 15, the packet is discarded.
  • Routing updates are broadcast every 30 seconds, by default.

Interior Gateway Routing Protocol (IGRP) is a proprietary protocol developed by Cisco. Some of the IGRP key design characteristics emphasize the following:

  • It is a distance vector routing protocol.
  • Bandwidth, load, delay and reliability are used to create a composite metric.
  • Routing updates are broadcast every 90 seconds, by default.

Open Shortest Path First (OSPF) is a nonproprietary link-state routing protocol. The key characteristics of OSPF are as follows:

  • It is a link-state routing protocol.
  • Open standard routing protocol described in RFC 2328.
  • Uses the SPF algorithm to calculate the lowest cost to a destination.
  • Routing updates are flooded as topology changes occur.

EIGRP is a Cisco proprietary enhanced distance vector routing protocol. The key characteristics of EIGRP are as follows:

  • It is an enhanced distance vector routing protocol.
  • Uses load balancing.
  • Uses a combination of distance vector and link-state features.
  • Uses Diffused Update Algorithm (DUAL) to calculate the shortest path.
  • Routing updates are broadcast every 90 seconds or as triggered by topology changes.

Border Gateway Protocol (BGP) is an exterior routing protocol. The key characteristics of BGP are as follows:

  • It is a distance vector exterior routing protocol.
  • Used between ISPs or ISPs and clients.
  • Used to route Internet traffic between autonomous systems.
 

Interactive Media Activity

Checkbox: Link-State and Distance Vector Routing Protocols

After completing this activity, the student will be able to understand IP routing protocols.

 
 

Web Links

Introduction to IP Routing

http://www.cisco.com/en/US/tech/tk365/tech_topology
_and_network_serv_and_protocol_suite_home.html