IP Routing

BYMr.Sourabh Badve

Chapter Objectives

Explain Protocols Explain Routing Metrics Discuss Routing Mechanisms Explain Routing Algorithms Set up routing

Recall

The router configuration files are located in: RAM NVRAM TFTP Server

Protocol that gives the information about locally attached and remote devices in the network is termed as Cisco Discovery Protocol (CDP)

CDP global parameters include: CDP timer CDP holdtime

Goals of Routing

Routing process ensures that appropriate packets are 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

IP Routing with One Router

IP Routing with Three Routers

Process of Routing Packets within a Router

Routing Metrics

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

Different routing metrics include: Hops Bandwidth Load Cost Reliability

Dynamic Routing

The phenomena in which the routing protocols are assigned 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

Administrative Distance

An integer assigned to every routing protocol, which determines the reliability of the routing protocol is termed as administrative distance (AD)

The integer is in the range of 0 to 255 Lower the AD, more reliable is the routing

information provided by the routing protocol

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)

Interior Routing Protocols

The protocols used to route the packets inside an autonomous 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)

Exterior Routing Protocols

The routing protocols that communicate between the two or more Autonomous Systems (AS) are termed as Exterior routing protocols

Exterior Routing Protocols include: Exterior Gateway Protocols (EGP) Border Gateway Protocol (BGP)

Routing Tables The routing tables then decide the best path to the

route the packet, which also includes the next hop address

Information contained in the routing table include: Destination Next hop address Outgoing interface Routing Protocols

Static Routing

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

This is feasible in small networks, but not in large networks

Routing Information Protocol (RIP) RIP allows routers to exchange their routing tables

at a predefined interval Characteristics of RIP include:

Uses hop count metric Supports 15 hop-count limit Supports six equal-cost paths

Distance Vector concept

The routers connected to the neighboring networks update 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

RIP Timers

RIP timers are used to keep a track of the various routes connected

The different RIP timers include: Route update timer Route invalid timer Holddown timer Route Flush timer

Enhancements in RIPv2

RIPv2 was created to overcome the drawbacks of RIPv1

RIPv2 enhancements include: Multicasting Triggered updates Classless protocol Authentication

Case Study

The Hyderabad branch of the Blue Diamond Steel Company 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 the networks. 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 the company to add five more networks to the existing ones.

Problem

The network administrator has to manually add routes to all the networks connected and then

send the packets

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 as its metric to route the packets and can be used to

connect small networks

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 on

their routing abilities as: Interior Routing Protocols Exterior Routing Protocols

Summary - II

Interior Routing protocols can be classified as: Routing Information Protocol (RIP) 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)

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 µ symbol

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 are

implemented on a router to determine the best path to route the packets

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

Summary - VI

Enhancements in RIPv2 include: Supports multicast updates against broadcast

updates Uses triggered updates to share its routing

information 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