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Sunday, January 13, 2013

CCDA Notes: Network Design Methodology

Network Design Basics

Business forces that affect decisions for enterprise network include:

  • Return on Investment - Cost savings or increased productivity
  • Regulation - Meet industry regulations (HIPAA, DOD, etc)
  • Competitiveness - Technology needs to make business more competitive

Technology forces which affect decisions for network include:

  • Removal of borders - Network resources must be accessible from more places than before, like branch offices, teleworkers, mobile devices and business partners
  • Virtualization - Reduction in hardware/power/software needs as well as space considerations by virtualizing many services
  • Growth of Applications - As applications become larger and more demanding of resources, network resources are required to adapt
IT optimization areas can be split into three groups:
  1. Data Centers
  2. Networks
  3. Applications
Three architectures provide for optimization within each group and inter-group as well:

  • Borderless Networks Architecture
  • Collaboration Architecture
  • Data Center/Virtualization Architecture

Borderless Networks Architecture

  1. Policy/Control: Policies applied across all users/devices
  2. Network Services: Resiliency and control
  3. User Services: Services include performance, mobility, security
  4. Connection Management: Delivers secure access anytime/anywhere

Collaboration Architecture

  1. Communication/Collaboration Apps: conferencing, messaging, mobile apps, IP comms, social software
  2. Collaboration Services: Services that supports the collaboration apps: policy/security management, contact management, session management, location, presence, client framework
  3. Infrastructure: Allows collaboration anytime/anywhere on any device. This layer includes virtual machines, the network and storage.

Data Center/Virtualization

Data center/virtualization architecture is built on Cisco Data Center 3.0, which has a set of virtualization technologies/services that bring network/storage/computing/virtual platforms together

PPDIOO: The Cisco Lifecycle

  • Lowers cost of ownership by validating tech requirements, planning for infrastructure changes/resource requirements
  • Increases network availability through good network design
  • Improves business by establishing technology strategies/business requirements
  • Speeds access to applications through improved availability, reliability, scalability, security and performance
Lowering Cost Of Ownership:
  • Identify/validate tech requirements
  • Plan for infrastructure changes/resource requirements
  • Develop network design to mesh with business/technology needs
  • Improve network efficiency
  • Reduce operating expense by streamlining processes/tools
Increasing Network Availability
  • Assess the network and its ability to support design
  • Choose correct hardware/software and keep current
  • Create good network design and verify operation
  • Staging/testing before implementation
  • Improving engineer skills
  • Proactively monitor network for issues
  • Proactively identify security issues and remediation plan

Improve Business
  • Establish business/technology requirements
  • Ready sites to support design
  • Integrate technical needs and business needs into design
  • Expertly install system components
  • Continue to enhance performance after implementation
Speed Application Access
  • Improve operational readiness for current/planned network technology/service
  • Increase availability, capacity and performance of network
  • Manage/resolve issues affecting system, keep software current

 PPDIOO Phases:

Prepare Phase

Establish requirements, develop network strategy, propose high-level network architecture


Plan Phase

Identify requirements by assessing current network and perform gap analysis between current/proposed


Design Phase

Provide high availability, scalability, reliability, security and performance in design


Implement Phase

Install/configure new equipment

Operate Phase

Analyze daily network operations and operational health


Optimize Phase

Proactive network management, propose modifications to design as needed


Design Methodology

1. Identify Customer Requirements

Identify network apps/services

  • Planned Applications
  • Concrete applications
  • Importance to business
  • Other Info/Comments
Define goals of organization, such as:
  • Increase competitiveness in field
  • Reduce costs
  • Improve customer relations (Better support, new services)
Identify possible constraints
  • Budget
  • Timeframe
  • Limited personnel
  • Policy limitation
Define technical goals
  • Improve network speed
  • Decrease failures
  • Simply management of network
  • Improve security
  • Improve scalability
  • Improve reliability
  • Tech refresh
Identify possible technical constraints
  • Legacy applications
  • Bandwidth allocation may not meet application needs
  • Existing infrastructure
  • Legacy equipment


2. Assess Current Network

  • Identify/Gather existing documentation about organization/network
  • Audit network to determine details of network
  • Analyze traffic for applications/protocols used

Identify/Gather Documentation

Include site designs, contacts, hours of operation/access and addresses, where network equipment is located and what infrastructure exists. Also gather info about LAN/WAN wiring and contact info for WAN providers. Especially look for IP/Vlan schema and IP allocation information, as well as network applications and servers in use

Network Audit

Use existing documentation, existing network management tools, and new tools to covers gaps in analysis. Audit should provide following:
  •  List/naming convention for network devices
  • Hardware info for network devices
  • Software versions for network info as well as supported applications
  • Network configs
  • LAN/WAN speeds of vital links
  • Auditing tool output
  • WAN technology/provider info
Manual Analysis: review device configs, manually use show commands and collect output
  • show tech-support
  • show version
  • show log
  • show running-config
  • show process cpu
  • show process memory
  • show interface
Network Analysis Tools: Inspects packets for data flow/traffic analysis
  • Netform DesignXpert Enterprise: Desktop tool to discover/design/quote/propose solutions
  • CNS NetFlow Collector: Cisco hardware that collects network info
  • Cisco Embeded Resource Manager: Monitors IOS processes/utilization
  • Third-party tools: SolarWinds, NeTMRI, etc
After audit, check to make sure the following is true before moving on with design:
  • Network segments should be switched, not using hubs
  • WAN links are not saturated (70% or higher)
  • Response time acceptable (Generally 2ms on LAN, less than 100ms on WAN)
  • No segemts have more than 20% multi/broadcast traffic
  • No segment has more than 1 CRC per MB of data
  • Less than .1% of packets collide on ethernet segments
  • Network devices shouldn't have 75% CPU utilization for 5 min or over
  • Interface output drops shouldn't exceed 100 per hour
  • Interface input queue drops shouldn't exceed 50 per hour
  • Interface buffer misses shouldn't exceed 25 per hour
  • Interface ignored packets shouldn't exceed 10 per hour
  • QoS should be enabled for prioritization

3. Designing Network and Solutions


Start from top layer of OSI model and work downward, adapt infrastructure for application requirements. Analyze application requirements for top layers (Application, Preentation, Session) and develop infrastructure to support it for bottom layers (Transport, Network, Data Link, Physical)

  • Design meets current/future needs and organization requirement
  • Far more time-consuming


Start from bottom of OSI model and build upward. Utilize best practice and previous implementation experience to design network without taking specific application requirements into account

  • Allows for quick solution, based on best practice/previous experience
  • May be inappropriate design, may not meet specific requirements

Develop Design Document

  • Introduction: Describe project's purpose and reasoning
  • Design Requirement: List requirements, constraints and goals
  • Existing Network Infrastructure: Include logical topology diagram, audit results, summary list of appications, etc
  • Design: Specific design info, logical/physical topology, IP/Vlan Schema, routing protocols, security, etc
  • Proof of Concept: Results from prototype/pilot testing
  • Implementation Plan: Detailed steps for network staff to implement design
  • Appendixes: List of network devices, configs, additional info
Implementation Plan should include several phases with each phase containing:
  • Description of phase
  • Reference to design
  • Detailed implementation guidelines
  • Detailed rollback guidelines if implementation fails
  • Estimated time to implement

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