Basic Router Configuration

BYMr.Sourabh S. Badve

Chapter Objectives

Explain IGRP Explain EIGRP Explain OSPF

Recall - I The different metrics used by the routing protocols

include: Hops Bandwidth Load cost Reliability

Interior routing protocols include: Routing Information Protocol (RIP) Open Shortest Path First (OSPF) Interior Gateway Routing Protocol (IGRP)

Recall - II Enhanced Interior Gateway Routing Protocol

(EIGRP) Intermediate System to Intermediate System (IS – IS)

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

Routing tables can be defined as the database that contains the routing information of the network

Interior Gateway Routing Protocol (IGRP) IGRP is a distance-vector routing protocol The characteristics if IGRP include:

Uses composite metric Supports unequal-cost load balancing Supports multipath routing Supports holddowns Supports split horizons

Verifying IGRP Commands to verify IGRP configurations include:

show ip route show protocols show ip protocols debug ip rip debug ip igrp events debug ip igrp transactions

Debugging IGRP The debugging command displays the routing

information and the updates sent and received on the router

Commands for debugging IGRP include: debug ip igrp events debug ip igrp transactions

Enhanced Interior Gateway Routing Protocols (EIGRP) EIGRP saves all the routes connected to the

neighboring routers EIGRP has the qualities of both distance-vector and

link state protocols EIGRP is an ideal protocol in the large networks

Diffusing Update Algorithm (DUAL) DUAL helps the router to determine the best route to

the destination using the hop count, bandwidth and other factors as metrics

It sends query packets to the neighboring routers to determine the best path to reach the destination network

When a router receives a reply, DUAL calculates the successor (main route) and the feasible successor (backup route)

Route Discovery and Maintenance For discovering the routes, the tables used by

EIGRP include: Neighbor table Topology table Route table Successors Feasible successors

Unlike the other protocols, EIGRP uses four metrics, bandwidth, delay, load and reliability to determine the best path to transmit the packets

Verifying EIGRP Commands to verify EIGRP configurations include:

show ip route show ip route eigrp show ip eigrp neighbors show ip eigrp topology

Border Gateway Protocol BGP is an Exterior Gateway Protocol used to

exchange the routing information between two or more Autonomous Systems (AS)

It uses cost as its metrics The hosts that use BGP as their routing protocol,

exchange information with the help of TCP/IP It uses the method of Classless Inter-Domain

Routing (CIDR)

Link State Routing Protocols In Link-state routing, the routers while

communicating share the status of the links on the network

The protocols send Link State Advertisement (LSA) that contains routing information and details of the router that sent the information

The destination router stores the LSAs in a local database

When a change occurs in the database, the router runs the Shortest Path First (SPF) algorithm

Open Shortest Path First (OSPF) OSPF uses the link-state concept and sends Link

State Advertisements (LSAs) to all the connected routers

Entities of the OSPF hierarchy include: Autonomous System (AS) Areas Backbone Area

Area Border Routers (ABRs) Stub Area Autonomous System Boundary Router (ASBRs)

OSPF Hierarchy

Case StudyThe Hyderabad branch of the Blue Diamond Steel Company has 15 routers connected in the network. The network uses RIP to route the packets between the departments. Now the company has decided to add a team of 20 Software Engineers to design the new steel plants. The network administrator has decided to place the engineers on a different network. This requires the 16th router to be placed in the network.

Problem

The other departments cannot exchange the data with the software engineers

Solution

The network administrator decided to use OSPF, which uses bandwidth as its metric to route the

packets and can be used to connect large networks

Intermediate System to Intermediate System (IS – IS) IS – IS is a link state routing protocol used to carry

IP network information The routing in IS – IS is carried out in two levels:

Level 1 comprises of the routers connected in an area

Level 2 comprises of routers connected to the routers in multiple areas

Verifying OSPF Commands to verify OSPF configurations include:

show ip route show ip ospf show ip ospf database show ip ospf interface show ip protocols

Summary - I IGRP is a distant-vector routing protocol, which

implies that each router sends all or a part of its routing table in a routing message update

The characteristics of IGRP are: Uses composite metric Supports unequal-cost load balancing Supports multipath routing Supports multipath routing Supports holdown Supports split horizons

Summary - II The characteristics of EIGRP are:

Fast convergence Link-state protocol Less network overhead Interoperation with IGRP Supports three routed protocols Six path load-balancing

The Open Shortest Path First (OSPF) is a link-state routing protocol, used to handle routing for Internet Protocol (IP) traffic

Summary - III The OSPF protocol is designed on the Shortest

Path First (SPF) algorithm, which enables to determine the shortest route to each destination

OSPF provides the following advantages: Open protocol Loop free topology Scalable Hierarchical design Provides multicasting

Summary - IV The OSPF maintains a two-layer hierarchy

consisting of: Backbone area Off backbone

The advantage of dividing OSPF into areas are as follows: Conserves router resources Concealing information Dealing with external routes

Summary - V There are different OSPF area types that help to

handle external routes: Normal area Stub area Totally stubby area Not-so-stubby area