OSI Network Layer
Network Fundamentals – Chapter 5
Version 4.0
© 2007 Cisco Systems, Inc. All rights reserved.
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1
What Did We Discover Last Class?
 Transport Layer
 Serial interfaces “flapping”
 TCP/IP vs UDP
 Configuring serial interfaces
 Connection oriented
 Hardware failures
 Connectionless
 Cabling problems
 Header overhead
 Well known Port numbers
© 2007 Cisco Systems, Inc. All rights reserved.
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2
What I will Learn

The role of the Network Layer, as it describes communication
from one end device to another end device.

Examine Internet Protocol (IP), and its features for providing
connectionless , best-effort service.

Understand the principles used to guide the grouping of devices
into networks.

Hierarchical addressing of devices and how this allows
communication between networks.

The fundamentals of routes, next hop addresses and packet
forwarding to a destination network.
© 2007 Cisco Systems, Inc. All rights reserved.
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3
Network Layer Protocols and Internet Protocol (IP)
© 2007 Cisco Systems, Inc. All rights reserved.
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4
Network Layer Protocols and Internet Protocol (IP)
© 2007 Cisco Systems, Inc. All rights reserved.
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5
Network Layer Protocols and Internet Protocol (IP)
© 2007 Cisco Systems, Inc. All rights reserved.
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6
Network Layer Protocols and Internet Protocol (IP)
© 2007 Cisco Systems, Inc. All rights reserved.
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7
Network Layer Protocols and Internet Protocol (IP)
© 2007 Cisco Systems, Inc. All rights reserved.
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8
Network Layer Protocols and Internet Protocol (IP)
© 2007 Cisco Systems, Inc. All rights reserved.
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9
Network Layer Protocols and Internet Protocol (IP)
© 2007 Cisco Systems, Inc. All rights reserved.
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10
Grouping Devices into Networks and Hierarchical
Addressing
© 2007 Cisco Systems, Inc. All rights reserved.
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11
Grouping Devices into Networks and Hierarchical
Addressing
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
12
Grouping Devices into Networks and Hierarchical
Addressing
© 2007 Cisco Systems, Inc. All rights reserved.
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13
Grouping Devices into Networks and Hierarchical
Addressing
Communication problems that emerge when very large numbers of devices are
included in one large network
© 2007 Cisco Systems, Inc. All rights reserved.
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14
Grouping Devices into Networks and Hierarchical
Addressing
Describe how hierarchical addressing solves the problem of devices communicating
across networks of networks
© 2007 Cisco Systems, Inc. All rights reserved.
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15
Grouping Devices into Networks and Hierarchical
Addressing
 The purpose of further subdividing networks into smaller networks
© 2007 Cisco Systems, Inc. All rights reserved.
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16
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
© 2007 Cisco Systems, Inc. All rights reserved.
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17
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
Tracert / traceroute
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18
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
The role of a gateway and the use of a simple route table in directing
packets toward their ultimate destinations
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
19
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
20
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
21
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
22
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
 Trace the steps of IP packets as they are routed through gateways from
devices on one network to devices on other networks
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
23
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
24
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
25
Fundamentals of Routes, Next Hop Addresses and
Packet Forwarding
Explain the role of routing protocols in building the routing table
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
26
What I will Learn

The role of the Network Layer, as it describes communication
from one end device to another end device.

Examine Internet Protocol (IP), and its features for providing
connectionless , best-effort service.

Understand the principles used to guide the grouping of devices
into networks.

Hierarchical addressing of devices and how this allows
communication between networks.

The fundamentals of routes, next hop addresses and packet
forwarding to a destination network.
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
27
OSI Network Layer
Next
Addressing the Network
© 2007 Cisco Systems, Inc. All rights reserved.
Cisco Public
28