Routing

Introduction

Distance Vector Concept

Distance Vector: Update

Distance Vector: Network Discovery

Distance Vector: Topology Change

Link State Concept

Link State: Update

Link State: Network Discovery

Link State: Topology Change

Interial and Exterior Routing

Routing Information Protocol (RIP)

Interior Gateway Routing Protocol (IGRP)

Open Shortest Path First (OSPF)

Border Gateway Protocol (BGP)

Enhanced IGRP (EIGRP)

Summary

Comparison

Link State vs Distance Vector

Reference

Untitled Document
Introduction

⊕ Static Routing

⊕ Dynamic Routing

♦ Distance Vector

      RIP、IGRP、BGP

♦ Link State

      OSPF、IS-IS

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Untitled Document
Distance Vector Concept
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Distance Vector: Update
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Distance Vector: Network Discovery
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Distance Vector: Topology Change
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Link State Concept
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Link State: Update
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Link State: Network Discovery
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Link State: Topology Change
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Interial and Exterior Routing
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Routing Information Protocol (RIP)

♦ Distance vector routing protocol

♦ Path weight: hop count

♦ If the hop count is greater than 15, the packet is discarded

♦ Routing updates are broadcast every 30 seconds, by default IGRP

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Interior Gateway Routing Protocol (IGRP)

♦ Distance vector routing protocol.

♦ Path Weight: Bandwidth, load, delay and reliability

♦ Routing updates are broadcast every 90 seconds, by default

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Open Shortest Path First (OSPF)

♦ Link-state routing protocol

♦ Uses the SPF algorithm to calculate the lowest cost to a destination.

♦ Routing updates are flooded as topology changes occur

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Border Gateway Protocol (BGP)

♦ Distance vector exterior routing protocol.

♦ Used between ISPs or ISPs and clients.

♦ Used to route Internet traffic between autonomous systems

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Enhanced IGRP (EIGRP)

♦ 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.

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Summary
Protocol Description Charateristics
Distance Vector RIPv1 and RIPv2

Interior Gatway Routing Protocol(IGRP)

  • Coupies routing table to neighbors
  • Update frequently
  • RIPv1 and RIPv2 use hpos counts as metric
  • View network's topology from neighbor's perspective
  • Slow to converge
  • Susceptible to routing loops
  • Easy to configure and administer
  • Comsumes a lot of bandwidth
Link-State Open Shortest Path First(OSPF)

Intermediate-System to Intermediate-System(IS-IS)

  • Use shortest path
  • Update are event triggered
  • Send Link-State packets to all network routers
  • Event triggered upfates:faster convergence
  • Has common view of networks
  • Fast to converge
  • Not as susceptible to routing loops
  • Hard to configure
  • Require more memory and procrdding power
  • Comsumes less bandwidth
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Comparison
Distance Vector Link State
View network from neighbor's perspective Get common view of entire network topology
Add distance vectors form router to router Caculate the shortest path to other routers
Frequent periodic updates:
slow convergence 		Event triggered upfates:
faster convergence
Passes copies of routing tables to neighbor routers Passes Link-State routing updates to other routers
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Link State vs Distance Vector
Advantages Disadvantages
Fast convergence: changes are reported immediately by the source affected Significant demands on memory and processing resources
Robustness against routing loops Requires very strict network design
Routers know the topology Requires a knowledgeable network administrator
Link-state packets are sequenced and aged Initial flooding can impede network performance
The link-state database sizes can be minimized with careful network design
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Reference

♦ www.cisco.com

♦ Cisco CCNA e-Learning

♦ Cisco CCNP e-Learning

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