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IP Routing

BY

Mr.Sourabh Badve


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Chapter Objectives

Explain Protocols

Explain Routing Metrics

Discuss Routing Mechanisms

Explain Routing Algorithms

Set up routing


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Goals of Routing

Routing process ensures that appropriate packetsare routed from the source to the destination

Goals of routing include:

Stability

Provides with a robust network

Dynamic update of the network paths

Information is safe while transmitting


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IP Routing with One Router


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IP Routing with Three Routers


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Process of Routing Packets within a

Router


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Routing Metrics

Routing metrics are values that allow the routersdecide the best route for the data packet

Different routing metrics include:

Hops

Bandwidth

Load

Cost

Reliability


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Dynamic Routing

The phenomena in which the routing protocols areassigned the job of finding the path to route the

packets and update the routing tables

Two types of dynamic routing protocols include:

Interior routing protocols

Exterior routing protocols


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AD of Routing Protocols

Routed Source Default AD

Connected Interface 0

Static Route 1

Enhanced Interior Gateway Routing Protocol

(EIGRP)

90

Interior Gateway Routing Protocol (IGRP) 100

Open Shortest Path First (OSPF) 110

Routing Information Protocol (RIP) 120

External EIGRP 170

Unknown 255 (This route will never be

used)


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Interior Routing Protocols

The protocols used to route the packets inside anautonomous system, are termed as Interior Routing

protocols

Interior routing protocols include:

Routing Information Protocol (RIP)

Open Shortest Path First (OSPF)

Interior Gateway Routing Protocol (IGRP)

Enhanced Interior Gateway Routing Protocol(EIGRP)

Intermediate System to Intermediate System (IS IS)


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Exterior Routing Protocols

The routing protocols that communicate betweenthe two or more Autonomous Systems (AS) are

termed as Exterior routing protocols

Exterior Routing Protocols include:

Exterior Gateway Protocols (EGP)

Border Gateway Protocol (BGP)


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Routing Tables

The routing tables then decide the best path to theroute the packet, which also includes the next hop

address

Information contained in the routing table include:

Destination

Next hop address

Outgoing interface

Routing Protocols


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Static Routing

The phenomena of adding routes manually to therouting table, is termed as static routing

This is feasible in small networks, but not in large

networks


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RIP allows routers to exchange their routing tablesat a predefined interval

Characteristics of RIP include:

Uses hop count metric

Supports 15 hop-count limit

Supports six equal-cost paths


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Distance Vector concept

The routers connected to the neighboring networksupdate the list of networks and the hop counts in the

routing table

The connected routers update the routing table with

the network information

The routers connected to the distant networks

construct a new routing table

The network information of the connected routers

combined with the new routing table entries is

passed to all the neighboring routing tables


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RIP Timers

RIP timers are used to keep a track of the variousroutes connected

The different RIP timers include:

Route update timer

Route invalid timer

Holddown timer

Route Flush timer


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Enhancements in RIPv2

RIPv2 was created to overcome the drawbacks ofRIPv1

RIPv2 enhancements include:

Multicasting

Triggered updates

Classless protocol

Authentication


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Case Study

The Hyderabad branch of the Blue Diamond SteelCompany has 10 routers connected in the network.

Initially, the network administrator had configured the

network to use static routes to route the packets

containing the data and to communicate between thenetworks. Now the company has decided employ

more than 100 employees for their operations in

Software Management, Human Resource, Detailing,

Business Development and Sales. This requires thecompany to add five more networks to the existing

ones.


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Problem

The network administrator has to manually add

routes to all the networks connected and then

send the packets


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Solution

The network administrator decided to use RIP, which

is a dynamic routing protocol. It can add the routes

to the network automatically and uses hop count asits metric to route the packets and can be used to

connect small networks


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Summary - I

Routing occurs at the network layer of the OSI

model

Protocols are a set of rules that define data transfer

The routing protocols can be classified based ontheir routing abilities as:

Interior Routing Protocols

Exterior Routing Protocols


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Summary - II

Interior Routing protocols can be classified as:


Open Shortest Path First (OSPF)

Interior Gateway Routing Protocol (IGRP) Enhanced Intermediate System to Intermediate

System (EIGRP)

Intermediate System to Intermediate System

Exterior Routing protocols can be classified as: Exterior Gateway Protocol (EGP)

Border Gateway Protocol (BGP)


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Summary - III

Routing metrics are cost values that enable routers

decide the best route for the data packet

When a router forwards a data packet to a network

segment, it is counted as a single hop

Bandwidth measures the amount of data that can

travel over the network segment in a fixed amount of

time

Delay specifies the amount of time that a router takes

to process and transfer a data packet to the next

device on the network

The delay is represented with a symbol


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Summary - IV

Load refers to the amount of traffic on a particular link

relative to the total capacity of the link

The load value 255 indicates 100% traffic congestion

Direct interfaces consist of routes that are local to the

router

Routed protocols consist of protocols that define

routing and addressing

Routing protocols are a set of rules that areimplemented on a router to determine the best path to

route the packets


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Summary - V

Routing protocols can be classified into Interior

Routing Protocols and Exterior Routing Protocols

Every router has a routing table based on which the

data packets are forwarded to the destinations

Static routes are the routes that the administrator

manually enters in the routing table

Static routes are used in temporary connections

such as dial-up networks The router automatically collects and stores dynamic

routes in the routing table


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Summary - VI

Enhancements in RIPv2 include:

Supports multicast updates against broadcast

updates

Uses triggered updates to share its routinginformation with the neighbors, when a change

occurs

Supports Variable-Length Subnet Masking

(VSLM) Allows you to select the routers you want to

participate in RIPv2

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