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CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Introduction
Introduction
The Cisco Designing Cisco Network Service Architecture (ARCH)course helps prepare students for the Cisco Certified
Design Professional(CCDP) certification. Objectives for the ARCH course include the following:
n Explain Cisco Service-Oriented Enterprise Network Architecture (SONA).
n Discuss how SONA can be used for enterprise network design.
n Illustrate how to design functionality,performance,scalability,and availability into the various functional areas of
the enterprise network.
n Review network management,high availability,security,QoS,and IP multicast design considerations.
n Explain design principles for virtual private networks (VPNs) and wireless networks.
These Quick Reference Sheets summarize the main topics presented in the ARCH course materials. The information
presented represents the version of content on which exam number 642-873 bases its questions.
© 2008 Cisco Systems Inc. All rights reserved. This publication is protected by copyright.Please see page 98 for more details.
CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
Publisher: Cisco Press Licensed by Minh Dang
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CHAPTER 1 CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Cisco Design Models
Chapter 1: Cisco Design Models
This section introduces you to Ciscos Service-Oriented Network Architecture(SONA) framework for network design. In
addition,you learn how to use the PPDIOO approach to network design.
Service-Oriented Network Architecture
Cisco recently updated their 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 Voice over IP(VoIP) or storage networking,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.
Ciscos 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:(1) Networked Infrastructure Layer,(2) Infrastructure
Services Layer,and (3) Application Layer.
© 2008 Cisco Systems Inc. All rights reserved. This publication is protected by copyright.Please see page 98 for more details.
CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
Publisher: Cisco Press Licensed by Minh Dang
Print Publication Date: 2007/10/26 User number: 927500 Copyright 2007, Safari Books Online, LLC.
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CHAPTER 1 CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Cisco Design Models
FIGURE 1-1
SONA Layers ApplicationLayer Business Applications Collaboration Applications
InteractiveServicesLayer AppliIcnafrtiaosnt rNucettuwroer Skienrgv iSceesrvices AdaptiveManagementServices
NetworkedInfrastructureLayer CampSuesrver Branch DaStato Craegneter WAN/MAN ClieTenltesworker
SONA offers the following benefits to a network design:
n Functionality:Functions in a way that the design supports organizational requirements
n Scalability:Meets organizational growth demands
n Availability:Makes network services available consistently and reliably
n Performance:Offers acceptable responsiveness,bandwidth utilization,and throughput for applications
n Manageability:Offers administrators control over the network,monitoring of the network,and fault detection
within the network
n Efficiency:Meets design objectives within stated financial constraints
© 2008 Cisco Systems Inc. All rights reserved. This publication is protected by copyright.Please see page 98 for more details.
CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
Publisher: Cisco Press Licensed by Minh Dang
Print Publication Date: 2007/10/26 User number: 927500 Copyright 2007, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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[ 6]
CHAPTER 1 CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Cisco Design Models
PPDIOO
Cisco categorizes a network’s life cycle into six phases identified with the acronym PPDIOO,as follows:
n Prepare:This phase involves determining the network’s requirements,formulating a network strategy,and suggest-
ing a conceptual architecture of the network.
n Plan:This phase compares the existing network with the proposed network to help identify tasks,responsibilities,
milestones,and resources required to implement the design.
n Design:This phase clearly articulates the detailed design requirements.
n Implement:This phase integrates equipment into the existing network (without disrupting the existing network) to
meet design requirements.
n Operate:This phase entails the day-to-day network operation,while responding to any issues that arise.
n 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.
PPDIOO’s life-cycle approach offers the following benefits:
n PPDIOO reduces total cost of ownership(TCO).
n PPDIOO improves network availability.
n PPDIOO allows business networks to quickly respond to changing needs.
n PPDIOO accelerates access to network applications and services.
© 2008 Cisco Systems Inc. All rights reserved. This publication is protected by copyright.Please see page 98 for more details.
CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
Publisher: Cisco Press Licensed by Minh Dang
Print Publication Date: 2007/10/26 User number: 927500 Copyright 2007, Safari Books Online, LLC.
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CHAPTER 1 CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Cisco Design Models
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 understanding that the documentation might be somewhat
dated and unreliable),and interview organizational representatives to uncover information not available in the
documentation.
n Conduct a network audit to identify such information as network traffic types,congestion points,and subopti-
mal 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 Networking Services(CNS) NetFlow Collection Engine,Open Source Cacti,Network General Sniffer,
WildPackets EtherPeek and AiroPeek,SolarWinds Orion,Wireshark,and remote-monitoring(RMON) probes.
© 2008 Cisco Systems Inc. All rights reserved. This publication is protected by copyright.Please see page 98 for more details.
CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
Publisher: Cisco Press Licensed by Minh Dang
Print Publication Date: 2007/10/26 User number: 927500 Copyright 2007, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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CHAPTER 1 CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Cisco Design Models
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 recommends top-down design approach that assists the designer by breaking
the design process into smaller and more manageable steps. The term top-downrefers to beginning 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.
FIGURE 1-2 OSI Model
Top-Down Design
Strategy BeginDs eHseigrne Application
Presentation
Session
Remaining design Transport
considerations
sequentially
address lower layers
of the OSI model. Network
Data Link
Physical
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 also provides scalability
to meet future network enhancements
© 2008 Cisco Systems Inc. All rights reserved. This publication is protected by copyright.Please see page 98 for more details.
CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
Publisher: Cisco Press Licensed by Minh Dang
Print Publication Date: 2007/10/26 User number: 927500 Copyright 2007, Safari Books Online, LLC.
This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior
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[ 9]
CHAPTER 2 CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Network Design Considerations for the Enterprise Campus
Chapter 2: Network Design Considerations for the
Enterprise Campus
This section discusses Cisco design recommendations for an enterprise campus network. These networks need to support
evolving technologies such as IP telephony,storage-area networks,content networking,and application networking.
High-Availability Design
Constructing an enterprise campus network using modular building blocks can add to a network’s availability,in addition
to its scalability. Traditionally,Cisco prescribed a three-layer model for network designers. Those three layers,as shown
in Figure 2-1,are as follows:
n Access layer:Typically,wiring closet switches connecting to end-user stations
n Distribution layer:An aggregation point for wiring closet switches,where routing and packet manipulation occur,
and also where the campus network interconnects to remote networks
n Core layer:The network backbone where high-speed traffic transport is the main priority
© 2008 Cisco Systems Inc. All rights reserved. This publication is protected by copyright.Please see page 98 for more details.
CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
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[ 10]
CHAPTER 2 CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Network Design Considerations for the Enterprise Campus
FIGURE 2-1
Three-Layer Core Layer
Hierarchical Model
Distribution Layer
Access Layer
The goals of high availability are to minimize component failures (for example,network links or network endpoints) and
to minimize the time required to recover from a component failure. A common design approach for high-availability
networks is to fully mesh redundant switches located in the distribution and core layers. Recommended design strategies
for maximizing redundancy include the following:
n Alternate pathing:A single path between network devices represent a single point of failure.
n Redundant components:Convergence time for redundant access layer switches can be reduced by using the
following:
n Stateful switchover (SSO):Useful for both Layer 2 and Layer 3 access switches,SSO permits a backup route
processor to immediately take over control from a failed primary route processor.
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CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
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CHAPTER 2 CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Network Design Considerations for the Enterprise Campus
n Nonstop forwarding (NSF):Useful for Layer 3 access switches,NSF continues to forward packets after a
route processor switchover,until routing convergence completes.
n Software Modularity Architecture of Cisco IOS Software:Using Cisco IOS Software Modularity
Architecture,software patching can be performed without reloading the supervisor engine of a Catalyst 6500
series switch.
Layer 2 Design
Most commonly found at the access layer,Layer 2 components in an enterprise campus network need to be configured
for optimal convergence times. Layer 2 devices use the Spanning Tree Protocol(STP) for convergence,but Cisco recom-
mends that the use of STP be avoided because routing protocols (used by Layer 3 devices) can converge faster than STP.
However,some situations require the use of STP,for example:
n To support a VLAN that exists on multiple access layer switches
n To protect from loops being created between access layer ports
n To support certain server farm applications
Cisco offers a variety of enhancements to STP:
n PortFast:Allows an access port to bypass STPs listening and learning phases
n UplinkFast:Reduces STP convergence from 50 seconds to approximately 3 to 5 seconds
n BackboneFast:Reduces STP convergence time for an indirect link failure
n LoopGuard:Helps prevent loops that could occur because of a unidirectional link failure,a software failure,or a
bridge protocol data unit(BPDU) loss due to congestion
n RootGuard:Prevents an inappropriate switch from being elected as a root bridge
n BPDUGuard:Causes a port configured for PortFast to go into the errordisable state if a BPDU is received on the
port
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CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
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[ 12]
CHAPTER 2 CCDP ARCH Quick Reference by Kevin Wallace and Michael Watkins
Network Design Considerations for the Enterprise Campus
In addition,a variety of STP implementations are supported on many Cisco Catalyst switches:
n 802.1D:The original version of STP
n Common Spanning Tree (CST):Shares a common spanning-tree topology for multiple VLANs
n Per VLAN Spanning Tree Plus (PVST+):Ciscos proprietary approach to providing a separate spanning-tree topol-
ogy for each VLAN
n 802.1w:Rapid STP(RSTP),which reduces spanning-tree convergence times
n 802.1s:Multiple Spanning Tree(MST),which allows different VLANs to be mapped to one of multiple STP
instances,thus providing optimal pathing for each VLAN without necessitating an STP instance for each VLAN
If STP is used,Cisco recommends the following:
n Use LoopGuard on Layer 2 ports between distribution layer switches.
n Configure RootGuard on distribution layer switch ports that connect to access layer switches.
n Implement UplinkFast on access layer switch ports that connect to distribution layer switches.
n Use BPDUGuard,RootGuard,and PortFast on access layer switch ports that connect to end-user devices.
n Configure UniDirectional Link Detection(UDLD) to detect links that have failed in one direction.
n Implement port security,as needed,to limit the number of MAC addresses that can pass traffic through an access
layer switch port.
Layer 2 Catalyst switches also use trunks to carry traffic for multiple VLANs across a single physical connection. Cisco
recommends the following best practices for trunks:
n Configure IEEE 802.1Q trunks,as opposed to Inter-Switch Link(ISL) trunks.
© 2008 Cisco Systems Inc. All rights reserved. This publication is protected by copyright.Please see page 98 for more details.
CCDP ARCH Quick Reference
CCDP ARCH Quick Reference By Kevin Wallace, Michael Watkins ISBN: 9781587054990 Prepared for Minh Dang, Safari ID: [email protected]
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