CCNP_BSCI_Quick_Reference_Sheets_(Cisco-2007).pdf

The Evolving Network Model

EIGRP

OSPF

IS-IS

Optimizing Routing

CCNP BSCI

Quick Reference Sheets

Exam 642-901

BGP

IP Multicast

IPv6 Introduction

Brent Stewart

Denise Donohue

ciscopress.com

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ABOUT THE AUTHORS

CCNP BSCI Quick Reference Sheets

About the Authors

Brent Stewart, CCNP, CCDP, MCSE, Certified Cisco Systems Instructor, is a network administrator

for CommScope. He participated in the development of BSCI, and has seperately developed training

material for ICND, BSCI, BCMSN, BCRAN, and CIT. Brent lives in Hickory, NC, with his wife,

Karen and children, Benjamin, Kaitlyn, Madelyn, and William.

Denise Donohue, CCIE No. 9566, is a Design Engineer with AT&T. She is responsible for designing

and implementing data and VoIP networks for SBC and AT&T customers. Prior to that, she was a

Cisco instructor and course director for Global Knowledge. Her CCIE is in Routing and Switching.

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ICONS USED IN THIS BOOK

CCNP BSCI Quick Reference Sheets

Icons Used in This Book

Router

7507

Router

Multilayer Switch

with Text

Multilayer

Switch

Communication

Server

Switch

IDC

Internal Firewall

IDS

Web

Browser

Database

App Server

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CHAPTER 1

CCNP BSCI Quick Reference Sheets

The Evolving Network

Model

This same three-layer hierarchy can be used in the WAN with a central

headquarters, division headquarters, and units.

FIGURE 1-2 Three-Layer Network Design

The Hierarchical Design Model

Cisco used the three-level Hierarchical Design Model for years. This

older model provided a high-level idea of how a reliable network might

be conceived, but it was largely conceptual because it didn’t provide

specific guidance. Figure 1-1 shows the Hierarchical Design Model.

Core

Distribution

FIGURE 1-1 Hierarchical Design Model

Core

Access

Distribution

The layers break a network in the following way:

Access

n Access layer—End stations attach to the network using low-cost

devices.

n Distribution layer—Intermediate devices apply policies.

— Route summarization

Figure 1-2 is a simple drawing of how the three-layer model might

have been built out. A distribution layer-3 switch is used for each build-

ing on campus, tying together the access switches on the floors. The

core switches link the various buildings together.

— Policies applied, such as:

• Route selection

• Access lists

• Quality of Service (QoS)

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CHAPTER 1

THE EVOLVING NETWORK MODEL

CCNP BSCI Quick Reference Sheets

n Core layer—The backbone that provides a high-speed path

between distribution elements.

recommendations about how and where certain network functions should

be implemented. This model is based on the principles described in the

Cisco Architecture for Voice, Video, and Integrated Data (AVVID).

— Distribution devices are interconnected.

— High speed (there is a lot of traffic).

The Enterprise Composite Model (see Figure 1-3) is broken into three

large sections:

— No policies (it is tough enough to keep up).

Later versions of this model include redundant distribution, core

devices, and connections, which make the model more fault-tolerant.

n Enterprise Campus—Switches that make up a LAN

n Enterprise Edge—The portion of the enterprise network connected

to the larger world.

Problems with the Hierarchical Design Model

This early model was a good starting point, but it failed to address key

issues, such as:

n Service Provider Edge—The different public networks that are

attached

The first section, the Enterprise Campus, looks like the old Hierarchical

Design Model with added details. It features six sections:

n Where do wireless devices fit in?

n How should Internet access and security be provisioned?

n Campus Backbone—The core of the LAN

n How do you account for remote access, such as dial-up or VPN?

n Building Distribution—Links subnets/VLANs and applies policy

n Where should workgroup and enterprise services be located?

n Building Access—Connects users to network

n Management

Enterprise Composite Network

Model

The newer Cisco model—the Enterprise Composite Model—is significantly

more complex and attempts to address the shortcomings of the Hierarchical

Design Model by expanding the older version and making specific

n Edge Distribution—A distribution layer out to the WAN

n Server Farm—For Enterprise services

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