Cisco.Press.CCDA.Quick.Reference.Sheets.pdf

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INTRODUCTION

CCDA Quick Reference Sheets by Kevin Wallace

Introduction

The Cisco Designing for Cisco Internetwork Solutions (DESGN) exam

is the required exam for the Cisco Certified Design Associate (CCDA)

certification. Objectives for the DESGN exam include the following:

n Describe a systematic and modular approach to design.

n Design enterprise campus, enterprise data center, enterprise edge,

and remote modules.

n Assign an appropriate IP addressing scheme.

n Select an appropriate routing protocol.

n Specify security solutions.

n Provide support for voice traffic.

n Offer a solution for basic wireless connectivity.

These Quick Reference Sheets summarize the main topics presented on

the DESGN exam. The information presented represents the content

covered on exam number 640-863.

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CCDA Quick Reference Sheets by Kevin Wallace

Strategic Network Design

This section introduces you to the Cisco Service-Oriented Network

Architecture (SONA) framework for network design. In addition, you

learn how to examine characteristics of an existing network, while

determining design requirements. Finally, this section discusses Cisco’s

top-down approach to network design.

The Cisco architectural approach to designing an IIN is their SONA

framework. Figure 1-1 shows individual IIN components and how those

components are categorized by SONA’s three layers: networked infra-

structure layer, infrastructure services layer, and application layer.

Business Applications

Collaboration Applications

Application Networking Services

Cisco Service-Oriented

Network Architecture

Cisco recently updated its Architecture for Voice Video and Integrated

Data (AVVID) design approach to the Intelligent Information Network

(IIN). IIN is a complete architecture that is more all encompassing than

AVVID.

The three phases of constructing an IIN are as follows:

n Integrated transport —Voice, data, and video are all converged

onto a single transport.

n Integrated services —Services, such as VoIP or storage network-

ing, rely on the underlying network transport mechanisms.

n Integrated applications —Applications (for example, Cisco IP

Communicator) leverage services (for example, VoIP), which rely

on the network transport.

Infrastructure Services

Campus

Branch

Data Center

WAN/MAN

Teleworker

Server

Storage

Clients

FIGURE 1-1 SONA layers.

SONA offers the following benefits to a network design:

n Functionality

n Scalability

n Availability

n Performance

n Manageability

n Efficiency

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CCDA Quick Reference Sheets by Kevin Wallace

Identifying Design

Requirements

Cisco categorizes a network’s life cycle into six phases identified with

the acronym PPDIOO. The components of PPDIOO are as follows:

1. Prepare —This phase involves determining the network’s require-

ments, formulating a network strategy, and suggesting a concep-

tual architecture of the network.

2. Plan —This phase compares the existing network with the

proposed network to help identify tasks, responsibilities, mile-

stones, and resources required to implement the design.

3. Design —This phase clearly articulates the detailed design

requirements.

4. Implement —This phase integrates equipment into the existing

network (without disrupting the existing network) to meet design

requirements.

5. Operate —This phase entails the day-to-day network operation,

while responding to any issues that arise.

6. Optimize —This phase gathers feedback from the Operate phase

to potentially make adjustments in the existing network. Changes

might be implemented to address ongoing network support issues.

n PPDIOO allows business networks to quickly respond to changing

needs.

n PPDIOO accelerates access to network applications and services.

Designing a network in conjunction with the PPDIOO approach

involves three steps:

1. Identify customer requirements.

To identify customer requirements, obtain the following pieces of

information:

n Network applications

n Network services

n Business goals

n Constraints imposed by the customer

n Technical goals

n Constraints imposed by technical limitations

2. Identify characteristics of the current network.

To identify characteristics of the current network, perform the

following tasks:

n Collect existing network documentation (with the understand-

ing that the documentation might be somewhat dated and

unreliable), and interview organizational representatives to

uncover information not available in the documentation.

PPDIOO’s life-cycle approach offers the following benefits:

n PPDIOO reduces total cost of ownership (TCO).

n PPDIOO improves network availability.

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CCDA Quick Reference Sheets by Kevin Wallace

n Conduct a network audit to identify information such as

network traffic types, congestion points, and suboptimal

routes.

n Supplement the information collected in the two previous

tasks by performing a network traffic analysis with tools such

as Cisco Discovery Protocol (CDP), Network Based

Application Recognition (NBAR), NetFlow, Cisco CNS

NetFlow Collection Engine, Open Source Cacti, Network

General Sniffer, WildPackets EtherPeek and AiroPeek,

SolarWinds Orion, Wireshark, and Remote Monitoring

(RMON) probes.

OSI Model

Design begins here

Application

Remaining design

considerations

sequentially address

lower layers of the OSI

model

Presentation

Session

Transport

Network

Data Link

Physical

FIGURE 1-2 Top-down design strategy.

Using a top-down design strategy as opposed to a bottom-up design

strategy (that is, where the design begins at the physical layer of the

OSI model and works its way up) provides the following benefits:

n Does a better job of including specific customer requirements

n Offers a more clearly articulated “big picture” of the desired

network for both the customer and the designer

n Lays the foundation for a network that not only meets existing

design requirements but provides for scalability to meet future

network enhancements

3. Design the network topology.

Using information collected in Steps 1 and 2, you are ready to

begin your network design. Although designing a network can be

a daunting task, Cisco’s recommended top-down design approach

assists the designer by breaking the design process into smaller

and more manageable steps. The term top-down refers to begin-

ning at the top of the OSI reference model (that is, the application

layer) and working your way down through the underlying layers,

as shown in Figure 1-2.

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CCDA Quick Reference Sheets by Kevin Wallace

When using the OSI reference model in the top-down design

approach, the designer should determine what design decisions, if

any, are required for each of the seven layers. For example, when

considering the application layer, the designer might determine

that voice applications such as the Cisco IP Contact Center and the

Cisco Unity converged messaging system are applications needed

for the design.

Network layer design decisions might include the selection of a

routing protocol (for example, Enhanced Interior Gateway Routing

Protocol [EIGRP] or Open Shortest Path First Protocol [OSPF]).

Also, when analyzing the network layer, the designer might need

to determine an appropriate IP addressing scheme for the network

(for example, the use of private versus public IP addresses and

subnet masks to be used) to provide for future network scalability.

Physical layer and data link layer design decisions might involve

the selection of LAN/WAN technologies (for example, Gigabit

Ethernet, Fast Ethernet, Frame Relay, ATM, or PPP) to provide for

media transport.

With the multitude of design decisions required in larger networks,

network designers often benefit from network design tools such as

the following:

n Network modeling tools —Generate suggested configurations

based on input information, which can then be further customized

(for example, adding redundancy or support for additional sites)

n Strategic analysis tools —Enable a network designer to experi-

ment with various “what-if” scenarios and observe resulting

network effects

n Decision tables —Record design decisions based on network

requirements

n Simulation and verification tools/services —Verify design deci-

sions in a simulated environment to reduce the need to implement

a pilot network

Even with the availability of simulation tools, some network

designs still benefit from building a small prototype network to

serve as a proof of concept. Such prototype networks are

commonly known as pilot networks .

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