Chapter 5

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1Version 4.0
Creating the Network
Design
Designing and Supporting Computer Networks – Chapter 5

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 2
Objectives
 Analyze business goals and application requirements
to determine what factors affect the network design
 Utilize the hierarchical design model to develop a
cost-effective network design that matches the
organization’s requirements
 Select the appropriate WAN connectivity option to
meet the organization’s requirements
 Incorporate wireless connectivity into the LAN design,
based on the results of the wireless survey
 Incorporate security into the LAN/WAN design,
including placement of firewalls, IDS, and ACLs

Analyze Business Goals and Application
Requirements
 List business goals that must be met by the new design
 Decide which design elements must be present in the
final design
 Explore alternatives to constraints
 Make trade-offs

Requirements
Strategies for scalability:
 Access Layer modules
 Expandable, modular equipment
 Broadcast limitation
 Multiple links
 Localized VLANs

Requirements
Availability requirements:
 Affordable implementation, maximum protection from
failure
 Availability for e-commerce
 Security monitoring system
 IP telephone system

Requirements
Performance requirements:
 Transaction-processing
 Video distribution and monitoring
 IP telephone voice quality

Requirements
Security requirements:
 Use of firewalls
 VPNs
 Intrusion prevention
systems
 Endpoint security

Requirements
Design trade-offs:
 Accommodate business goals
 Eliminate or complicate other improvements

Utilize the Hierarchical Design Model to
Develop a Cost-Effective Network Design
Access Layer requirements:
 Connectivity for existing devices and new devices
 VLANs to separate voice, security, wireless, and
normal data services
 Redundancy
 QoS

 Capabilities of existing technology
 Limitations of existing equipment
 Power requirements

Distribution layer requirements:
 Redundant components and links
 High-density routing
 Traffic filtering
 QoS implementation
 High-bandwidth connectivity
 Fast convergence
 Route summarization

Core Layer requirements:
 High-speed connectivity
 Routed interconnections
 High-speed redundant
links

 Create the logical LAN diagram, including the locations
of servers and services

Select the Appropriate WAN Connectivity
Option
 Determine WAN services needed for remote sites

Option
 Select the appropriate WAN connectivity method and
identify the equipment required to support it

Option
 Backing up the Frame Relay link
 Supporting remote workers

Option
 Evaluate IP addressing and routing methodologies for
WAN traffic based on company requirements

Incorporate Wireless Connectivity into
the LAN Design
 Identify the appropriate wireless equipment and
capabilities to meet specific design requirements

the LAN Design
Integrating wired and wireless solutions:
 Lightweight Access Points (LAPs)
 Wireless LAN controllers

the LAN Design
Factors influencing availability in a wireless network:
 Location of the AP
 Signal strength of the AP
 Number of users
 Dynamic reconfiguration
 Centralization

the LAN Design
Create an IP address scheme for a wireless LAN:
 Layer 3 roaming

Incorporate Security into the LAN/WAN
Design
 Determine the source and nature of potential threats
 Draw a diagram of the placement of security functions
and filters

Primary categories of security services:
 Infrastructure protection
 Secure connectivity
 Threat detection, defense, and mitigation
Design

Design
Design and implement the appropriate access filters to
meet a specific network security requirement:
 Firewall rule sets
 Access control lists

Design
Include access control lists and firewall rules in the
design documentation:
 Provide evidence that the security policy is
implemented
 Ensure that when changes are made, existing rules are
known
 Assist in troubleshooting

Summary
 For each business goal, the designer determines what
network changes are necessary.
 Converged networks carry a combination of data, voice,
and video traffic.
 Designing WAN connectivity requires evaluation of the
telecommunications services available in the
customer’s area.
 Unified wireless network solutions offer advanced
features.
 The network designer must identify which data is at risk
and what the potential sources of attacks are.

Chapter 5

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