The document discusses several interior gateway routing protocols: IGRP is a distance-vector protocol that uses a composite metric and supports unequal-cost load balancing and multipath routing. EIGRP is a hybrid link-state and distance-vector protocol that provides fast convergence, less overhead, and supports six path load balancing. OSPF is a link-state protocol that uses the Shortest Path First algorithm to determine the shortest route and provides advantages like being open, loop-free, scalable, and hierarchical with multicasting support. It maintains a two-layer hierarchy of backbone and off-backbone areas to conserve router resources and handle external routes.

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Basic Router Configuration
Chapter 7

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Chapter Objectives
 Explain IGRP
 Explain EIGRP
 Explain OSPF

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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)

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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

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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

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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

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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

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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

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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)

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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

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Verifying EIGRP
 Commands to verify EIGRP configurations include:
 show ip route
 show ip route eigrp
 show ip eigrp neighbors
 show ip eigrp topology

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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)

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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

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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)

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OSPF Hierarchy

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Case Study
The 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.

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Problem
The other departments cannot exchange the data with
the software engineers

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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

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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

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Verifying OSPF
 Commands to verify EIGRP configurations include:
 show ip route
 show ip ospf
 show ip ospf database
 show ip ospf interface
 show ip protocols

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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

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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

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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

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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

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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