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IP Routing
Chapter 6
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Chapter 6 2
Chapter Objectives
Explain Protocols
Explain Routing Metrics
Discuss Routing Mechanisms
Explain Routing Algorithms
Set up routing
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Chapter 6 3
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
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Chapter 6 4
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
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Chapter 6 5
IP Routing with One Router
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Chapter 6 6
IP Routing with Three Routers
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Chapter 6 7
Process of Routing Packets within a
Router
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Chapter 6 8
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
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Chapter 6 9
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
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Chapter 6 10
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
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Chapter 6 11
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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Chapter 6 12
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)
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Chapter 6 13
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)
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Chapter 6 14
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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Chapter 6 15
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
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Chapter 6 16
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
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Chapter 6 18
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
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Chapter 6 19
Enhancements in RIPv2
RIPv2 was created to overcome the drawbacks of
RIPv1
RIPv2 enhancements include:
Multicasting Triggered updates
Classless protocol
Authentication
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Chapter 6 20
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 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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Chapter 6 21
Problem
The network administrator has to manually add
routes to all the networks connected and then
send the packets
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Chapter 6 22
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
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Chapter 6 23
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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Chapter 6 24
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)
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Chapter 6 25
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 takesto process and transfer a data packet to the next
device on the network
The delay is represented with a symbol
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Chapter 6 26
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 therouter
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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Chapter 6 27
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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Chapter 6 28
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