Ccna3 intro wan

Copyright 2003 www.ciscopress.com

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CCNA 3 Chapter 1

Review: The OSI Reference Model and Routing


Objectives• Describe the overall function of the OSI

reference model and the problems it solves • Describe the characteristics of the:

– OSI physical layer– OSI data link layer– OSI network layer– OSI transport layer

• Describe the function of routing in networks• Understand the different classes of routing

protocols


Benefits of the OSI Model?


OSI Layers with Purpose


Peer-to-Peer Communication


Data Encapsulation


Types of Ethernet• Ethernet and IEEE 802.3 — LAN specifications,

which operate at 10 Mbps over coaxial and twisted-pair cable.

• 100-Mbps Ethernet — A single LAN specification, also known as Fast Ethernet, which operates at 100 Mbps over twisted-pair cable.

• 1000 Mbps Ethernet — A single LAN specification, also known as Gigabit Ethernet, which operates at 1000 Mbps (1 Gbps) over fiber and twisted-pair cables.

• 10 Gigabit Ethernet is only supported over fiber optic media.


Three Varieties of 10 Mbps Ethernet

• 10BASE-2

– Known as thin Ethernet or thinnet

– Allows network segments up to 185 meters on coaxial cable

• 10BASE-5

– Known as thick Ethernet or thicknet

– Allows network segments up to 500 meters on coaxial cable

• 10BASE-T

– Carries Ethernet frames on inexpensive twisted-pair wiring


Encapsulation


The Physical Layer


The Data Link Layer

The Ethernet/802.3 Interface


Comparing Models


Address Classes


Address Class Prefixes


Subnetting Chart


Layer 3 Addresses - Path and Host Information


ICMP Testing


How ARP Works


Routing Table


IGP vs. EGP


Path Determination


Network and Host Addressing


Path Selection and Packet Switching


Network Layer Devices in Data Flow


Routing Metrics


Routed Versus Routing Protocol


Path Switching

The network layer (3) address does not change. The data link layer (2) MAC address changes for each segment.


Static Versus Dynamic Routes

• The purpose of a static route• Why dynamic routing is necessary• Dynamic routing operations• How distances on network paths are

determined by various metrics• Classes of routing protocols• Time for convergence


Static Versus Dynamic Routes


Dynamic Routing Operations


Routing Protocols

• A routing protocol defines the set of rules used by a router when it communicates with neighboring routers, including the following: – How to send updates – What knowledge these updates contain– When to send this knowledge – How to locate recipients of the updates


Time to Convergence


Distance Vector Routing Basics

• Routing updates explained• The problem of routing loops• The problem of counting to infinity• Link-state routing basics• How link-state protocols exchange routing

information• How topology changes propagate through the

network of routers


Distance Vector Routing Basics


Distance Vector Discovery


Distance Vector Topology Changes


Routing Metric Components


Link-State Routing Basics


Counting to Infinity


Split Horizon


Route Poisoning


Link-State Network Discovery


Link-State Topology Changes


Link-State Concerns


Distance Vector Versus Link State


Hybrid Protocols

Cisco’s EIGRP


The Transport Layer

• Segmenting upper-layer applications• Establishing a connection• Data transfer• Reliability with windowing• Acknowledgment techniques


"Reliable" Transport


Three-Way Handshake


Data Transfer


Windowing – Flow Control


Positive Acknowledgment

Education

Ccna3 intro wan