Knowledgenet Building Scalable Cisco Internetworks Bsci Student Guide v2.2

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BSCI

Building Scalable Cisco Internetworks Volumes 1 & 2 Version 2.2

Student Guide CLS Production Services: 06.29.05

Copyright 2005, Cisco Systems, Inc. All rights reserved. Cisco Systems has more than 200 offices in the following countries and regions. Addresses, phone numbers, and fax numbers are listed on the Cisco Website at www.cisco.com/go/offices. Argentina • Australia • Austria • Belgium • Brazil • Bulgaria • Canada • Chile • China PRC • Colombia • Costa Rica Croatia • Cyprus • Czech Republic • Denmark • Dubai, UAE • Finland • France • Germany • Greece Hong Kong SAR • Hungary • India • Indonesia • Ireland • Israel • Italy • Japan • Korea • Luxembourg • Malaysia Mexico • The Netherlands • New Zealand • Norway • Peru • Philippines • Poland • Portugal • Puerto Rico • Romania Russia • Saudi Arabia • Scotland • Singapore • Slovakia • Slovenia • South Africa • Spain • Sweden • Switzerland Taiwan • Thailand • Turkey • Ukraine • United Kingdom • United States • Venezuela • Vietnam • Zimbabwe Copyright 2005 Cisco Systems, Inc. All rights reserved. CCSP, the Cisco Square Bridge logo, Follow Me Browsing, and StackWise are trademarks of Cisco Systems, Inc.; Changing the Way We Work, Live, Play, and Learn, and iQuick Study are service marks of Cisco Systems, Inc.; and Access Registrar, Aironet, ASIST, BPX, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Empowering the Internet Generation, Enterprise/Solver, EtherChannel, EtherFast, EtherSwitch, Fast Step, FormShare, GigaDrive, GigaStack, HomeLink, Internet Quotient, IOS, IP/TV, iQ Expertise, the iQ logo, iQ Net Readiness Scorecard, LightStream, Linksys, MeetingPlace, MGX, the Networkers logo, Networking Academy, Network Registrar, Packet, PIX, Post-Routing, Pre-Routing, ProConnect, RateMUX, ScriptShare, SlideCast, SMARTnet, StrataView Plus, SwitchProbe, TeleRouter, The Fastest Way to Increase Your Internet Quotient, TransPath, and VCO are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries. All other trademarks mentioned in this document or Website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0501R) DISCLAIMER WARRANTY: THIS CONTENT IS BEING PROVIDED “AS IS.” CISCO MAKES AND YOU RECEIVE NO WARRANTIES IN CONNECTION WITH THE CONTENT PROVIDED HEREUNDER, EXPRESS, IMPLIED, STATUTORY OR IN ANY OTHER PROVISION OF THIS CONTENT OR COMMUNICATION BETWEEN CISCO AND YOU. CISCO SPECIFICALLY DISCLAIMS ALL IMPLIED WARRANTIES, INCLUDING WARRANTIES OF MERCHANTABILITY, NON-INFRINGEMENT AND FITNESS FOR A PARTICULAR PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. This learning product may contain early release content, and while Cisco believes it to be accurate, it falls subject to the disclaimer above.

Table of Contents Volume 1 Course Introduction 1 Overview Learner Skills and Knowledge 1 Course Goal and Objectives 2 Course Flow Additional References Cisco Glossary of Terms 4 Your Training Curriculum

1

3 4 5

Advanced IP Addressing 1-1 Overview Module Objectives

1-1 1-2

Using an IP Addressing Plan 1-3 Overview Objectives What Is a Scalable Network Design? 1-4 What Are the Benefits of Good Network Design? 1-10 What Are the Benefits of an Optimized IP Addressing Plan? 1-14 Example: Scalable Network Addressing 1-16 Update Size Unsummarized Internetwork Topology Changes 1-17 Summarized Network Topology Changes 1-18 Summary

1-3 1-3

1-17

1-19

Using Variable-Length Subnet Masks 1-21 Overview Objectives What Is the Prefix Length and Network Mask? 1-22 Example: Prefix Length and Network Mask 1-23 Calculating the Network Mask 1-25 Example: Range of Addresses for VLSM 1-27 Designing and Implementing a Scalable IP Address Plan 1-28 Example: Breakdown Address Space for Ethernets at Remote Sites 1-30 Example: Calculating VLSM–Binary 1-33 Summary

1-21 1-21

1-34

Using Route Summarization and CIDR 1-35 Overview Objectives What Is Route Summarization? 1-36 Example: What Is Route Summarization? 1-36 Calculating Route Summarization 1-38 Example: Summarizing Addresses in a VLSM-Designed Network 1-40 What Is CIDR? Example: What Is CIDR? 1-42 Example: CIDR Summary

1-35 1-35

1-41 1-43 1-44

Understanding IPv6 1-45 Overview Objectives What Is IPv6? What Is IPv6 Addressing? 1-48 Examples: Multiple ISPs and LANs with Multiple Routers 1-51 What Is the IPv6 Frame Format? 1-56

1-45 1-45 1-46

What Is IPv6-to-IPv4 Interoperability? 1-61 Summary Module Summary Module Self-Check Module Self-Check Answer Key 1-77

1-67 1-68 1-69

Routing Principles 2-1 Overview Module Objectives

2-1 2-1

Introducing IP Routing 2-3 Overview Objectives What Are Static Routing Principles? 2-4 Example: Configuring Static Routing 2-6 Configuring a Static Default Route 2-7 Example: Configuring a Static Default Route 2-7 What Are Dynamic Routing Principles? 2-8 Example: Configuring RIP to Run on Routers A and B 2-9 What Are ODR Principles? 2-10 Configuring ODR Example: Configuring ODR 2-13 Summary

2-3 2-3

2-12 2-14

Introducing Routing Protocols 2-15 Overview Objectives What Are Classful Routing Protocols? 2-16 What Is Automatic Summarization Using Classful Routing Protocols? 2-17 Example: Network Summarization in Classful Routing 2-18 What Is a Classful Routing Table? 2-20 Example: IP Routing Table 2-20 What Are Classless Routing Protocol Concepts? 2-22 Example: Classless Subnetting Requirements 2-23 What Is Network Summarization Using Classless Routing Protocols? 2-24 Example: Automatic Network Boundary Summarization 2-25 What Are the Effects of the auto-summary Commands? 2-26 Example: Effect of the auto-summary Command 2-26 Example: Disabling Automatic Summarization in RIP 2-27 What Is RIPv1? Configuring RIPv2 Example: Configuring RIPv2 2-33 Summary

2-15 2-15

2-28 2-29 2-34

Comparing IP Routing Protocols 2-35 Overview Objectives What Is Administrative Distance? 2-36 Example: Administrative Distance 2-37 Creating Floating Static Routes 2-38 Example: Floating Static Routes 2-39 Inserting Routes in the IP Routing Table 2-40 What Is IP Routing and Forwarding Architecture? 2-42 Comparing Routing Protocols 2-44 Summary Module Summary Module Self-Check Module Self-Check Answer Key 2-59

ii Building Scalable Cisco Internetworks (BSCI) v2.2 Copyright © 2005, Cisco Systems, Inc.

2-35 2-35

2-48 2-49 2-50

Configuring EIGRP 3-1 Overview Module Objectives

3-1 3-2

Introducing EIGRP 3-3 Overview Objectives What Is EIGRP? What Are the EIGRP Databases? 3-6 Example: Feasible Distance vs. Advertised Distance 3-9 Performing EIGRP Metrics Calculation 3-10 Example: EIGRP Metric Calculation 3-14 Summary

3-3 3-3 3-4

3-16

Using EIGRP 3-17 Overview Objectives What Are EIGRP Packets? 3-18 What Are Hello Packets? 3-19 Establishing Neighbors Maintaining EIGRP Databases and Neighbor Relationships 3-23 Example: Resetting of EIGRP Neighbors 3-26 Exchanging Initial Routing Information 3-27 Verifying EIGRP Connectivity 3-28 Example: Verifying EIGRP Connectivity Unstable Network 3-30 Example: Verifying EIGRP Operations Stable Network 3-31 Example: Verifying EIGRP Operations Unstable Network 3-32 Summary

3-17 3-17

3-21

3-33

Introducing EIGRP DUAL 3-35 Overview Objectives Selecting a Successor by DUAL 3-36 Example: EIGRP Successor 3-38 Selecting a Feasible Successor by DUAL 3-39 Example: EIGRP Feasible Successor 3-39 Example: Feasible Successor Route 3-40 Performing Route Selection When No Feasible Successor Is Available 3-41 What Is the EIGRP Query Process? 3-42 Example: Start Example: Link Goes Down 3-43 Summary

3-35 3-35

3-42 3-49

Configuring and Verifying EIGRP 3-51 Overview Objectives Configuring Basic EIGRP 3-52 Example: Configuring EIGRP for IP 3-54 Example: Wildcard Mask in EIGRP 3-56 Using and Configuring the default-network Command for EIGRP 3-57 Example: default-network Command 3-58 Verifying the EIGRP Configuration 3-59 Example: Verifying EIGRP 3-63 Summary

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3-51 3-51

3-65

Configuring Advanced EIGRP Options 3-67 Overview Objectives Configuring Manual Route Summarization 3-68 Example: Summarizing EIGRP Routes 3-71 What Is Load Balancing Across Equal Paths? 3-72 Configuring Load Balancing Across Unequal-Cost Paths 3-73 Example: Variance Configuring EIGRP Bandwidth Utilization 3-76 Example: WAN Configuration–Pure Point-to-Point 3-79 Example: WAN Configuration–Hybrid Multipoint 3-80 Summary

3-67 3-67

3-74

3-81

Using EIGRP in a Scalable Network 3-83 Overview Objectives Responding to a Query 3-84 Example: Limiting Updates and Queries 3-87 About Scalability Issues and Solutions 3-91 Limiting the EIGRP Query Range with Route Summarization 3-92 Example: Query Range–Summarization 3-94 Example: Limiting Updates and Queries 3-95 Limiting the EIGRP Query Range Using the Stub Option 3-97 Example: Limiting Updates and Queries 3-100 Identifying Scalability Rules 3-101 Example: Nonscalable Network Addressing 3-101 Example: Scalable Network Addressing 3-102 Summary Module Summary Module Self-Check Module Self-Check Answer Key 3-114

3-83 3-83

3-103 3-104 3-105

Configuring OSPF 4-1 Overview Module Objectives

4-1 4-1

Introducing OSPF 4-3 Overview Objectives What Are Link-State Routing Protocols? 4-4 About OSPF Areas What Are OSPF Adjacencies? 4-10 Calculating OSPF Example: SPF Calculation 4-14 Summary

4-3 4-3 4-7 4-13 4-16

Understanding OSPF Packet Types 4-17 Overview Objectives About OSPF Packet Types 4-18 Establishing OSPF Neighbor Adjacencies 4-20 Exchanging and Synchronizing LSDBs 4-22 Maintaining Link-State Sequence Numbers 4-28 Example: LSA Sequence Numbers and Maximum Age 4-29 Verifying OSPF Packet Flow 4-30 Example: debug ip ospf packet 4-30 Summary

iv Building Scalable Cisco Internetworks (BSCI) v2.2 Copyright © 2005, Cisco Systems, Inc.

4-17 4-17

4-32

Configuring Basic OSPF 4-33 Overview Objectives Configuring Basic Single-Area OSPF 4-34 Example: Configuring OSPF on Internal Routers of a Single Area 4-36 Manipulating the OSPF Router ID 4-42 Summary

4-33 4-33

4-46

Introducing OSPF Network Types 4-47 Overview Objectives What Is the Adjacency Behavior for a Point-to-Point Link? 4-48 What Is the Adjacency Behavior for a Broadcast Network Link? 4-49 What Is the Adjacency Behavior for an NBMA Network? 4-53 What Are the Configuration Options for OSPF over Frame Relay? 4-55 Example: Sample Configuration of a Frame Relay Router 4-58 What Are the OSPF and Frame Relay Configuration Strategies? 4-59 Example: neighbor Command 4-61 Example: show ip ospf neighbor Command 4-62 Example: Point-to-Multipoint Configuration 4-64 Example: Multipoint Subinterface 4-70 Example: OSPF over NBMA Topology Summary 4-71 What Is the Output from the debug Command? 4-72 Example: Partial debug Output 4-72 Example: Partial debug ip ospf adj Output 4-73 Summary

4-47 4-47

4-74

Using OSPF Routers and LSAs 4-75 Overview Objectives What Are the OSPF Router Types? 4-76 Example: OSPF Hierarchical Routing 4-77 What Are the OSPF LSA Types? 4-79 Type 1 Type 2 Types 3 and 4 Type 5 Type 6 Type 7 Type 8 Types 9, 10, and 11 4-80 Example: LSA Type 4—Summary LSA 4-84 Interpreting the OSPF LSDB and Routing Table 4-86 Example: Interpreting the OSPF Database 4-86 Example: Changing the Cost Metric 4-92 Summary

4-75 4-75

4-79 4-79 4-80 4-80 4-80 4-80 4-80

4-93

Configuring OSPF Route Summarization 4-95 Overview Objectives What Is OSPF Route Summarization? 4-96 Example: Using Route Summarization 4-98 Configuring OSPF Route Summarization 4-99 Example: Route Summarization Configuration at ABR 4-101 Example: Route Summarization Configuration at ASBR 4-102 What Are the Benefits of a Default Route in OSPF? 4-103 Example: Default Routes in OSPF 4-103

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4-95 4-95

Configuring a Default Route Injection into OSPF 4-104 Example: Default Route Configuration 4-106 Summary

4-107

Configuring OSPF Special Area Types 4-109 Overview Objectives What Are OSPF Area Types? 4-110 Configuring Stub Areas 4-112 Example: OSPF Stub Area Configuration 4-114 Configuring Totally Stubby Areas 4-115 Example: Totally Stubby Configuration 4-117 Example: Routing Tables with Different Areas 4-118 Example: Route Summarization, Stub Areas, and Totally Stubby Areas 4-119 Configuring Not-So-Stubby Areas 4-120 Example: NSSA Configuration 4-121 Example: NSSA Totally Stubby Configuration 4-122 Example: show Commands for Stub and NSSA 4-123 Summary

4-109 4-109

4-124

Configuring OSPF Virtual Links 4-125 Overview Objectives What Is an OSPF Virtual Link? 4-126 Configuring OSPF Virtual Links 4-128 Example: OSPF Virtual Link Configuration 4-130 Example: Virtual Link Backup Strategy 4-131 Example: show ip ospf virtual-links Command 4-132 Verifying OSPF Virtual Links 4-133 Summary Module Summary Module Self-Check Module Self-Check Answer Key 4-155

4-125 4-125

4-134 4-135 4-137

Volume 2 Configuring the IS-IS Protocol 5-1 Overview Module Objectives

5-1 5-2

Introducing IS-IS Routing and CLNS 5-3 Overview Objectives What Is IS-IS Routing? What Is Integrated IS-IS? 5-5 What Is ES-IS Protocol? 5-10 What Are OSI Routing Levels? 5-11 IS-IS Level 0 Routing 5-11 IS-IS Level 1 Routing 5-12 IS-IS Level 2 Routing 5-12 IS-IS Level 3 Routing 5-12 Summary What Are the Differences Between IS-IS and OSPF? 5-13 Summary

5-3 5-3 5-4

5-12 5-20

Understanding CLNS Addressing 5-21 Overview Objectives What Are NSAP Addresses? 5-22 What Are NET Addresses? 5-27 vi Building Scalable Cisco Internetworks (BSCI) v2.2 Copyright © 2005, Cisco Systems, Inc.

5-21 5-21

Summary

5-29

Operating IS-IS in a CLNS Environment 5-31 Overview Objectives What Are Intra-Area and Interarea Addressing and Routing? 5-32 Example: Identifying Systems—OSI Addressing in Networks 5-34 What Are IS-IS Routing Levels? 5-35 Example: OSI Area Routing 5-36 What Are IS-IS Protocol Data Units? 5-38 Example: OSI IS-IS PDUs 5-39 What Are Link-State Packets? 5-40 Example: LSP TLV Examples 5-42 What Are the Network Topologies? 5-44 What Are Broadcast Networks? 5-45 What Are the Levels in Point-to-Point Networks? 5-48 Level 1 and Level 2 LSP 5-48 Level 1 and Level 2 IIH 5-49 What Is Link-State Database Synchronization? 5-50 Example: Comparing Broadcast and Point-to-Point Topologies 5-50 Example: LSDB Synchronization LAN 5-53 Example: LSDB Synchronization Point-to-Point 5-54 Summary

5-31 5-31

5-57

Operating Integrated IS-IS in an IP and CLNS Environment 5-59 Overview Objectives What Is Integrated IS-IS NET Addressing? 5-60 Selecting Paths for IS-IS Area Routing 5-62 Building an IP Forwarding Database 5-63 Example: Building an IP Forwarding Table 5-64 Verifying CLNS IS-IS Structures 5-65 Example: OSI Intra-Area and Interarea Routing 5-67 Example: Simple Troubleshooting 5-71 Example: Establishing Adjacencies 5-72 Summary

5-59 5-59

5-73

Configuring Basic Integrated IS-IS 5-75 Overview Objectives What Are the Steps to Configure Integrated IS-IS? 5-76 Example: Simple Integrated IS-IS Configuration 5-81 Optimizing IS-IS Example: Tuning IS-IS Configuration 5-85 Configuring Route Summarization Within IS-IS 5-86 Verifying IS-IS Configuration 5-87 Example: Is Integrated IS-IS Running? 5-87 Summary Module Summary References Module Self-Check Module Self-Check Answer Key 5-100

5-75 5-75

5-82

5-89 5-90 5-90 5-91

Manipulating Routing Updates 6-1 Overview Module Objectives

6-1 6-1

Selecting Routes Between Multiple IP Routing Protocols 6-3 Overview Copyright

2005, Cisco Systems, Inc. Building Scalable Cisco Internetworks (BSCI) v2.2 vii

6-3

Objectives Migrating to Another Routing Protocol 6-4 Example: Migrating to a New Routing Protocol 6-5 Planning for New IP Address Allocation 6-6 Example: Planning the IP Address Transition 6-7 Migrating to a New IP Address Space 6-8 Example: Configuring a Secondary IP Address 6-9 Migrating to a New Routing Protocol 6-10 What Is Route Redistribution? 6-12 Example: Redistributing Route Information 6-15 What Are Seed Metrics? 6-16 Example: Seed Metrics 6-17 Example: Default Seed Metrics 6-18 Implementing Redistribution 6-19 Summary

6-3

6-22

Configuring and Verifying Route Redistribution 6-23 Overview Objectives Configuring Redistribution 6-24 Example: Redistribution Supports All Protocols 6-24 Redistributing Routes into RIP 6-26 Example: Configuring Redistribution into RIP 6-26 Example: Redistributing into RIP 6-28 Redistributing Routes into OSPF 6-29 Example: Configuring Redistribution into OSPF 6-29 Example: Redistributing into OSPF 6-31 Redistributing Routes into EIGRP 6-32 Example: Configuring Redistribution into EIGRP 6-32 Example: Redistributing into EIGRP 6-34 Redistributing Routes into IS-IS 6-35 Example: Configuring Redistribution into IS-IS 6-35 Example: Redistributing into IS-IS 6-37 Verifying Route Redistribution 6-38 Example: Before Redistribution 6-38 Example: Routing Tables Before Redistribution 6-39 Example: Configuring Redistribution 6-40 Example: Routing Tables After Route Redistribution 6-41 Summary

6-23 6-23

6-43

Controlling Routing Update Traffic 6-45 Overview Objectives Configuring a Passive Interface 6-46 Example: Using the passive interface Command 6-47 Configuring Route Filtering Using Distribute Lists 6-48 Example: Using Route Filters 6-50 Implementing the Distribute List 6-51 Summary

6-45 6-45

6-55

Using Route Maps to Control Routing Updates 6-57 Overview Objectives What Are Route Maps? 6-58 Example: Route Map Operation 6-62 Using route-map Commands 6-63 Implementing Route Maps with Redistribution 6-66 Example: Route Maps and Redistribution Commands 6-66 Example: Redistribution with Route Maps 6-67 Summary viii Building Scalable Cisco Internetworks (BSCI) v2.2 Copyright © 2005, Cisco Systems, Inc.

6-57 6-57

6-68

Using Administrative Distance to Influence the Route Selection Process 6-69 Overview Objectives What Is Administrative Distance? 6-70 Example: Administrative Distance 6-71 Modifying Administrative Distance 6-72 What Is the Impact of Administrative Distance Changes? 6-74 Example: Redistribution Using Administrative Distance 6-74 Example: Configurations for the P3R1 and P3R2 Routers 6-75 Example: Routing Table After Redistribution 6-76 Example: Knowing Your Network 6-79 Summary

Using PBR Overview Objectives PBR Benefits Establishing PBR Route Maps 6-84 Configuring PBR Example: PBR Equal Access 6-93 Verifying PBR Example: Verifying PBR 6-97 Example: Using the debug ip policy Command 6-98 Summary Module Summary Module Self-Check Module Self-Check Answer Key 6-114

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6-69 6-69

6-80

6-81 6-81 6-81 6-82 6-93 6-95

6-99 6-100 6-101

Configuring Basic BGP 7-1 Overview Module Objectives

7-1 7-1

Introducing BGP 7-3 Overview Objectives How Does BGP Route Between Autonomous Systems? 7-4 How Does BGP Use Path-Vector Functionality? 7-6 Example: BGP Policy-Based Routing 7-8 What Is BGP? What Are BGP Message Types? 7-13 Summary

7-3 7-3

7-9 7-15

Understanding BGP Concepts and Terminology 7-17 Overview Objectives Terminology for BGP Neighbor Relationships 7-18 Establishing External BGP Neighbor Relationships 7-19 Establishing Internal BGP Neighbor Relationships 7-20 Example: Internal BGP 7-20 Using Full Mesh of IBGP Neighbors 7-21 Example: IBGP and Redistribution 7-21 Example: Routing Issues Without Fully Meshed IBGP 7-24 Summary

7-17 7-17

7-26

Configuring Basic BGP Operations 7-27 Overview Objectives Configuring Basic BGP Operations 7-28 Example: BGP neighbor Command 7-32 Example: BGP Using Loopback Addresses 7-36 Example: ebgp-multihop Command 7-38 Example: Next Hop on a Multiaccess Network 7-41 Example: next-hop-self Configuration 7-43 Example: Peer Group 7-45 Example: BGP Synchronization 7-50 Example: BGP Configuration 7-51 Example: BGP Configuration for Router B 7-52 Identifying BGP Neighbor States 7-54 Example: BGP Session Establishment 7-55 Troubleshooting BGP Example: The debug ip bgp Command 7-66 Summary

7-27 7-27

7-59 7-68

Configuring Route Summarization with BGP 7-69 Overview Objectives What Is the Relationship Between BGP Version 4 and CIDR? 7-70 Example: CIDR and Aggregate Addresses 7-71 Example: Network Boundary Summarization 7-73 Using the network Command 7-74 Example: Cautions About Network Statements 7-76 Example: BGP Summarization Using the network Command 7-77 Using the aggregate-address Command 7-78 Example: BGP Summarization using the aggregate-address Command 7-80 Summary

x Building Scalable Cisco Internetworks (BSCI) v2.2 Copyright © 2005, Cisco Systems, Inc.

7-69 7-69

7-83

Selecting a BGP Path 7-85 Overview Objectives What Are the Characteristics of BGP Attributes? 7-86 What Is the AS Path Attribute? 7-90 Example: AS Path Attribute 7-90 What Is the Next-Hop Attribute? 7-91 Example: Next-Hop Attribute 7-91 What Is the Origin Attribute? 7-92 What Is the Local Preference Attribute? 7-93 Example: Local Preference Attribute 7-93 What Is the MED Attribute? 7-94 Example: MED Attribute 7-94 What Is the Weight Attribute? 7-95 Example: Weight Attribute (Cisco Only) 7-95 Determining the BGP Path Selection 7-96 Selecting a BGP Path Summary

7-85 7-85

7-97 7-99

Using Route Maps to Manipulate Basic BGP Paths 7-101 Overview Objectives Setting Local Preference with Route Maps 7-102 Example: BGP Is Designed to Implement Policy Routing 7-103 Example: BGP Route Selection Decision Process 7-104 Example: Setting a Default Local Preference 7-107 Example: Local Preference Case Study 7-108 Example: Default Settings on Router C 7-109 Example: Route Map for Router A 7-111 Setting the MED with Route Maps 7-113 Example: BGP Using the Default MED 7-114 Example: BGP Using Route Maps and the MED 7-115 Summary

7-101 7-101

7-119

Implementing Design Options for Multihoming 7-121 Overview Objectives What Are Design Choices with Multihoming for BGP? 7-122 Benefits of Default Route from Each Provider 7-124 Example: Default Routes from All Providers 7-126 Benefits of Partial Routing Table from Each Provider 7-127 Example: Default Routes from All Providers and Partial Table 7-128 Benefits of Full Routing Table from Each Provider 7-130 Example: Full Routes from All Providers 7-131 Example: Run BGP on Core Routers 7-132 Example: Filter BGP Advertisements to ISPs 7-133 Summary Module Summary References Module Self-Check Module Self-Check Answer Key 7-149

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7-121 7-121

7-134 7-135 7-136 7-137

BSCI

Course Introduction Overview Building Scalable Cisco Internetworks (BSCI) v2.2 is recommended training for individuals seeking Cisco CCNP certification. The course instructs network administrators of medium-tolarge network sites on the use of advanced IP addressing and routing in implementing scalability for Cisco routers that are connected to LANs and WANs. The goal is to train network administrators to dramatically increase the number of routers and sites using these techniques instead of redesigning the network when additional sites or wiring configurations are added.

Learner Skills and Knowledge This topic lists the skills and knowledge that learners must possess to benefit fully from the course. The subtopic also includes recommended Cisco learning offerings that learners should complete in order to benefit fully from this course.

Learner Skills and Knowledge • Cisco CCNA® certification

NOTE: Practical experience with deploying and operating networks based on Cisco network devices and Cisco IOS software is strongly recommended.

©2005 Cisco Systems, Inc. All rights reserved.

BSCI v2.2—3

Course Goal and Objectives This topic describes the course goal and objectives.

Course Goal

“To train network administrators on the techniques to plan, implement, and monitor a scalable IP routing network.” Building Scalable Cisco Internetworks

©2005 Cisco Systems, Inc. All rights reserved.

BSCI v2.2—4

Upon completing this course, you will be able to meet these objectives: Describe advanced IP addressing and implementation for scalable networks Describe advanced IP routing principles for scalable networks Configure and verify EIGRP with advanced features Configure and verify OSPF in a multiarea network Configure and verify IS-IS for IP and CLNS routing Manipulate routing and packet flow Configure and verify BGP for interdomain routing

2 Building Scalable Cisco Internetworks (BSCI) v2.2 Copyright © 2005, Cisco Systems, Inc.

Course Flow This topic presents the suggested flow of the course materials.

Course Flow Day 1Day 2Day 3Day 4Day 5

A M

Course Introduction Advanced IP Addressing

Configuring EIGRP

Configuring OSPF

Configuring the IS-IS Protocol

Configuring Basic BGP

Lunch

P M

Advanced IP Addressing

Configuring EIGRP

Configuring OSPF

Routing Principles

Configuring OSPF

Configuring the IS-IS Protocol

©2005 Cisco Systems, Inc. All rights reserved.

Manipulating Routing Updates

Configuring Basic BGP

BSCI v2.2—5

The schedule reflects the recommended structure for this course. This structure allows enough time for the instructor to present the course information and for you to work through the lab activities. The exact timing of the subject materials and labs depends on the pace of your specific class.

Copyright © 2005, Cisco Systems, Inc. Course Introduction 3

Additional References This topic presents the Cisco icons and symbols used in this course, as well as information on where to find additional technical references.

Cisco Icons and Symbols Cell Phone

Router

PDA Key

Network Cloud

Web Server

PC

File Server

Serial Link

Laptop Circuit-Switched Link

Ethernet End User

End User

©2005 Cisco Systems, Inc. All rights reserved.

BSCI v2.2—6

Cisco Glossary of Terms For additional information on Cisco terminology, refer to the Cisco Internetworking Terms and Acronyms glossary of terms at http://www.cisco.com/univercd/cc/td/doc/cisintwk/ita/index.htm.

4 Building Scalable Cisco Internetworks (BSCI) v2.2 Copyright © 2005, Cisco Systems, Inc.

Your Training Curriculum This topic presents the training curriculum for this course.

Cisco Career Certifications Expand Your Professional Options and Advance Your Career Cisco Certified Network Professional (CCNP)

Expert CCIE

Professional CCNP

Associate CCNA

Required Exam

Recommended Training Through Cisco Learning Partners

642-801 BSCI

Building Scalable Cisco Internetworks

642-811 BCMSN

Building Cisco Multilayer Switched Networks

642-821 BCRAN

Building Cisco Remote Access Networks

642-831 CIT

Cisco Internetwork Troubleshooting

http://www.cisco.com/go/certifications ©2005 Cisco Systems, Inc. All rights reserved.

BSCI v2.2—8

You are encouraged to join the Cisco Certification Community, a discussion forum open to anyone holding a valid Cisco Career Certification (such as Cisco CCIE ®, CCNA®, CCDA®, CCNP®, CCDP®, CCIP®, CCSP™, or CCVP™). It provides a gathering place for Ciscocertified professionals to share questions, suggestions, and information about Cisco Career Certification programs and other certification-related topics. For more information, visit http://www.cisco.com/en/US/learning/le3/le2/le37/learning_certification_level_home.html.

Copyright © 2005, Cisco Systems, Inc. Course Introduction 5

6 Building Scalable Cisco Internetworks (BSCI) v2.2 Copyright © 2005, Cisco Systems, Inc.

Module 1

Advanced IP Addressing Overview Scalable, well-behaved networks are not accidental; they are the result of good network design and effective implementation planning. A key element for effective scalable network implementation is a well-conceived and scalable advanced IP addressing plan. The purpose of an advanced IP addressing plan is to maximize the shrinking amount of IP address space available in deployed networks and minimize the size of routing tables. As a network grows, the number of subnets and the volume of network addresses increase proportionally. Without advanced IP addressing technique, such as summarization and classless interdomain routing (CIDR), the size of the routing table is increased, which causes a variety of problems; for example, the network requires more CPU resources to acknowledge each internetwork topology change in a larger routing table. In addition, larger routing tables have greater potential for delays when the CPU resources sort and search for a match to a destination address. Both of these problems are solved by summarization and CIDR. In order to effectively use summarization and CIDR to control the size of routing tables, network administrators employ advanced IP addressing techniques, such as Network Address Translation (NAT) and variable-length subnet masking (VLSM). NAT uses globally unique addresses for routing across the Internet and between independent divisions within an organization. NAT uses different address pools for tracking groups of users, which makes it easier to manage interconnectivity. VLSM is a type of subnet masking used for hierarchical addressing. This advanced IP addressing technique allows the network administrator to subnet a previously subnetted address to make the best use of the available address space. Another long-standing problem that network administrators must overcome is the exhaustion of available IP addresses caused by the increase in Internet use. Although the current solution is to use NAT, the long-term solution is to migrate from the IP version 4 (IPv4) 32-bit address space to the IP version 6 (IPv6) 128-bit address space. Gaining an insight into IPv6 functionality and deployment will prove valuable for network administrators in the not-too-distant future.

Module Objectives Upon completing this module, you will be able to describe advanced IP addressing and implementation for scalable networks. This ability includes being able to meet these objectives: Explain the benefits and characteristics of an effective scalable IP-addressing plan Calculate VLSM used in hierarchical addressing Describe the features and benefits of route summarization and CIDR Describe how IPv6 functions in order to satisfy the increasingly complex requirements of hierarchical addressing

1-2 Building Scalable Cisco Internetworks (BSCI) v2.2 Copyright © 2005, Cisco Systems, Inc.

Lesson 1

Using an IP Addressing Plan Overview A well-designed large-scale internetwork with an effective scalable IP addressing plan has many benefits. These benefits include a network that is scalable, flexible, predictable, and able to hide information through summarization. You must execute a detailed IP addressing plan to increase the scale of a network in an optimal manner and take advantage of the advanced features of current IP routing protocols.

Objectives Upon completing this lesson, you will be able to explain the benefits and characteristics of an effective scalable IP-addressing plan. This ability includes being able to meet these objectives: Describe the features of a scalable network design Describe the advantages of effective network design principles Describe the benefits of an optimized IP address planning

What Is a Scalable Network Design? This topic describes the features of a scalable network design.

Scalable Network Design

Access layer • Entry point for users into the internetwork

Distribution layer • Consolidation point for traffic and location of corporate resources

Core layer • Quick and efficient transit between divisions ©2005 Cisco Systems, Inc. All rights reserved.

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Corporate organizational structure affects the design of a network. The structure of scalable network design reflects the information flow of a corporation. These design structures are referred to as hierarchical network designs. Two types of hierarchical network design are as follows: Functional Geographical Within the context of these hierarchical networks, you must implement a scalable design at three network layers: the core layer, the access layer, and the distribution layer.

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Functional Structured Design

• Corporate networks may be organized by product divisions. • Network architecture can follow corporate organizational charts. ©2005 Cisco Systems, Inc. All rights reserved.

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Some corporations have independent divisions that are responsible for their own operations, including networking. These divisions interact with one another and share resources; however, each division has an independent chain of command. This type of corporate structure is reflected in a functional network design. A functional design internetworks various divisions according to their functional purpose within the corporate structure.

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Geographical Structured Design

Networks are organized along geographical boundaries such as countries or states. ©2005 Cisco Systems, Inc. All rights reserved.

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Many interstate retail corporations are organized by geographical location of retail stores. Within the corporate structure, each local retail store reports to a district consolidation point. These district consolidation points report to regional consolidation points. The regional consolidation points then report to corporate headquarters. This type of corporate structure is reflected in a geographical network design. A geographical design internetworks divisions according to their location. Note

From a networking point of view, a geographical network structure is cost-effective because fewer network links require long-haul carriers, often a considerable added expense.

Within the functional or geographical networks, the following three primary layer elements are involved in a scalable network design: Core layer: The circuits with the largest bandwidth are in the core layer of the network. Redundancy occurs more frequently at this layer than at the other layers. Access layer: The access layer is the entry point into the network for end users and customers. VLANs, firewalls, and access lists maintain security for this layer. Distribution layer: The distribution layer is the consolidation point for access-layer devices. Host services with multiple access-layer devices are assigned to this layer.

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Core Layer: Fully Meshed

• The core layer is designed to provide quick and efficient access to headquarters and other divisions within the company. • Redundancy is often found in the core network. • Compared to other layers, the core generally has the circuits with the largest bandwidth. ©2005 Cisco Systems, Inc. All rights reserved.

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In the fully meshed core-layer design, each division has redundant routers at the core layer. The core sites are fully meshed together. For a small core with a limited number of divisions, this core-layer design provides robust connectivity. However, a fully meshed core-layer design is very expensive for a corporation with many divisions. Note

In a fully meshed core-layer design, all routers have direct connections to all other nodes. This connectivity allows the network to react quickly when it must route data flow from a downed link to another pathway.

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Core Layer: Hub-and-Spoke

As the network grows, fully meshing all the core routers can become difficult. At that point, consolidation into geographically separate data centers is appropriate. ©2005 Cisco Systems, Inc. All rights reserved.

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The hub-and-spoke design configuration supports the traffic flow through the corporation. In many companies, the data travels to a centralized headquarters, where the corporate databases and network services reside. To reflect this corporate centralization, the core-layer hub-andspoke configuration establishes the focal point of the data flow as a key site.

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Access and Distribution Layers

Access layer • • •

Entry point for end users and customers into the network Security—VLANs, firewalls, access lists Addressing—DHCP

Distribution layer • •

Consolidation point for access-layer devices Hosts services that must be accessed by multiple access-layer devices

©2005 Cisco Systems, Inc. All rights reserved.

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Remote sites are points of entry to the network for end users and customers. Within the network, remote sites gain access to network services through the access layer. The distribution layer consolidates the services and devices that the access layer needs to process the activity that is generated by the remote sites. Place duplicating services at the distribution layer when there is no benefit in having duplicating services at the remote sites. These services may include Dynamic Host Configuration Protocol (DHCP), Domain Name System (DNS), human resources, and accounting servers. One or more distribution layers report to each entry point at the core layer. You can fully mesh connectivity between remote sites at the access layer. However, the huband-spoke configuration for remote sites reports to at least two corporate sites for administrative redundancy. Note

Frame Relay is the access protocol commonly used to interconnect geographically dispersed sites.

Copyright © 2005, Cisco Systems, Inc. Advanced IP Addressing 1-9

What Are the Benefits of Good Network Design? This topic describes the advantages of effective network design principles.

Benefits of an Optimized IP Addressing Plan and Design

• Scalability • Predictability • Flexibility ©2005 Cisco Systems, Inc. All rights reserved.

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An effective network design accommodates unexpected growth and quick changes in the corporate environment. The network responds to mergers with other companies, corporate restructuring, and downsizing with minimal impact on the portions of the network that do not change. The following are characteristics of good IP address plan implemented in a well-designed network: Scalability: A well-designed network allows for large increases in the number of supported sites. Predictability: A well-designed network exhibits predictable behavior and performance. Flexibility: A well-designed network minimizes the impact of routers, additions, changes, or removals within the network.

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Scalability with Good Design

• If one company merges with another company, where do you attach the additional routers? • If both companies were using network 10.0.0.0 for addressing, how would you overcome this obstacle and where would you implement the solution? ©2005 Cisco Systems, Inc. All rights reserved.

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The current proliferation of corporate mergers emphasizes the design issues inherent in private IP addressing (RFC 1918). A scalable network that integrates private addressing with a good IP addressing plan minimizes the impact of additions or reorganizations of divisions within a network. A scalable network enables companies that merge to connect at the core layer. Implementation of NAT on routers allows you to overlap network numbers and translate them to unused address space as a temporary solution. Then, overlapping network numbers can be changed on the PC or DHCP server. RFC 1918 has set aside the following IP address space for private use: Class A network: 10.0.0.0 to 10.255.255.255 Class B network: 172.16.0.0 to 172.31.255.255 Class C network: 192.168.0.0 to 192.168.255.255 Note

Private addressing is used exclusively for the examples in this course.

Good network design facilitates the process of adding routers to an existing network. In the example configuration, you can perform the following changes: Attach routers P and Q to the other routers in the core layer of the network Change the IP address space of the new company from network 10.0.0.0 to network 172.16.0.0 and configure NAT on routers P and Q Change the DHCP servers to reflect the newly assigned address space Remove NAT from routers P and Q

Copyright © 2005, Cisco Systems, Inc. Advanced IP Addressing 1-11

Predictability with Good Design

• The users behind routers B, C, and H are downloading 200 kbps per router from a server behind X. How much bandwidth do you need, and where do you place it to support this network? • If router D fails, which pathways handle the new load? ©2005 Cisco Systems, Inc. All rights reserved.

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The behavior of a scalable network is predictable. To gain predictability, bandwidth in a scalable network is equal to the higher-level site at each layer. For example, router C in the figure has the same bandwidth as routers B and E, so that router C fulfills load balancing. This load balancing allows access to networks behind routers B and E. Routers B and E are consolidation points for the access-layer routers (G, C, and F in the example). The pathways between routers B and E and routers A and D need larger-bandwidth pipes to consolidate the traffic between corporate divisions. Because routers A and D consolidate multiple distribution points for this division, the connections for these routers to other divisions in the company need the largest bandwidth. Use equal-cost paths for both hop count and bandwidth between any two routers in the internetwork; the packets load-balance across the internetwork. When a circuit or router fails, an alternate equal-cost path to the destination exists in every routing table. This alternate path limits convergence times and route recalculation to less than 1 second once a router discovers the failed circuit or router. Routing Information Protocol (RIP) is an effective tool for implementing predictability in a well-designed scalable network. For example, consider a network where router C uses equalcost hops to arrive at router X. The routing table for C has two best pathways to X: three hops through B and three hops through E. If router D fails, the routing table for router C does not change. Router B and router E each have two best pathways to the networks behind router X: both have two hops through either router A or router D. These routers do not discover alternate routes because the preferred route exists in the routing table. The result is a predictable traffic pattern. This level of network behavior predictability is a direct benefit of a scalable network design.

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Flexibility with Good Design

• Division B is sold and merged with another company, except for remote site H, which becomes part of Division A. How do you manage the transition? • What is the impact on the other divisions in the company? ©2005 Cisco Systems, Inc. All rights reserved.

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Corporate reorganizations have little impact on the rest of the network when implemented in a scalable network. For example, assume an example network that uses Frame Relay at the remote sites. The network administrator in the example network would accommodate a corporate reorganization with the following process: Step 1

Install two additional virtual circuits from router H to routers B and E.

Step 2

Following a successful installation, remove the virtual circuits to routers M and L.

Step 3

Perform NAT on the router H interfaces to routers E and B to use the address space of Division A.

Step 4

Remove the circuits from routers J and K to the other core routers A, D, P, Q, X, and Y.

Step 5

Change the user addresses for router H to the new block of addresses.

Copyright © 2005, Cisco Systems, Inc. Advanced IP Addressing 1-13

What Are the Benefits of an Optimized IP Addressing Plan? This topic describes the benefits of an optimized IP addressing plan.

Benefits of Hierarchical Addressing • Reduced number of route table entries: – Summarize multiple addresses into route summaries

• Efficient allocation of addresses: – Contiguous address assignment allows you to use all possible addresses

©2005 Cisco Systems, Inc. All rights reserved.

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The benefits of hierarchical addressing include the following: Reduced number of routing table entries: With Internet routers and internal routers, routing tables are as small as possible because of route summarization. In a hierarchical addressing plan, route summarization allows an IP address to represent a collection of IP addresses. Route summarization makes routing table entries manageable and provides the following benefits: —

More efficient routing

—

Reduced number of CPU cycles when recalculating a routing table or sorting through the routing table entries to find a match

—

Reduced router memory requirements

—

Faster convergence after a change in the network

—

Easier troubleshooting

Efficient allocation of addresses: Hierarchical addressing allows you to take advantage of all available addresses by grouping the addresses contiguously. With random address assignment, addressing conflicts waste address groups. For example, classful routing protocols automatically create summary routes at a network boundary. These protocols do not support discontiguous addressing, which makes some addresses unusable if they are not assigned contiguously.

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Within the context of hierarchical addressing, the IP network addressing plan must include provisions for summarization at key points. Summarization, or information hiding, is not a new concept. When a router announces a route to a given network, the route is a summarization of the addresses in the routing table for all the host devices and individual addresses that reside on that network. Summarization helps reduce routing table size. The use of summarization to reduce the size of the routing table helps localize topology changes, a benefit that promotes network stability. Network stability occurs because a reduced routing table size means reduced bandwidth use. It also reduces memory use and the number of CPU cycles that are required to calculate the best path selection.

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Scalable Network Addressing

• Each of the 50 divisions has 200 /24 subnets. • Each division summarizes its networks to 10. x.0.0 /16 on its core routers. • The routing table for any router has 200 /24 subnets plus 49 /16 summarized routers for a total of 249 entries in the IP routing table. ©2005 Cisco Systems, Inc. All rights reserved.

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Example: Scalable Network Addressing For this example, assume the following: A national drug store chain plans to have a retail outlet in every city in the United States with a population greater than 10,000. Each state has up to 100 stores, with two Ethernets in each store as follows: —

One Ethernet tracks customer prescriptions, pharmacy inventory, and reordering stock.

—

The second Ethernet stocks the rest of the store and ties the cash registers into a corporate-wide, instantaneous point-of-sale evaluation tool.

The total number of Ethernet networks is 10,000 because there are 100 stores in 50 states, each with two Ethernets (50 * 100 * 2 = 10,000). This total does not include an equal number of serial links that interconnect these stores. Using network address 10.0.0.0 and assigning a /24 subnet for each Ethernet creates an IP routing table of more than 10,000 subnets on each of the 5000 routers. On the other hand, by using a scalable design and creating 51 divisions (one for each state and one for the backbone interconnecting the division), the drugstore chain can assign each division a block of 10.x.0.0 /16. Each Ethernet has a /24 subnet of network 10.0.0.0, and each division has 200 subnets in the IP routing table of each router. When each division summarizes the block of network 10.x.0.0 /16 at the entry point to the core network, any router in a division can see the 200 /24 networks that represent the subnets for that division and 49 10.x.0.0 /16 summarizations that represent each additional division. This provides a total of 249 networks in each IP routing table.

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Nonscalable Network Addressing

• Poor addressing scheme does not use summarization. • Fifty divisions with 200 subnets each equals 10,000 entries in every routing table. • Which design—a scalable network with 249 entries or a nonscalable network with 10,000 entries —uses less CPU resources, memory, and bandwidth to announce its routing table? ©2005 Cisco Systems, Inc. All rights reserved.

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When you do not use summarization to assign IP addresses, problems occur. As shown in this figure, a network with 50 divisions in a scalable network with summarization has 249 routes in every routing table. The same network without summarization has 10,000 routes in every routing table. Why is the large number of routes a problem? The problems relate to the frequency and size of routing table updates and the way that topology changes are processed in summarized and unsummarized networks.

Update Size Routing protocols such as RIP and Interior Gateway Routing Protocol (IGRP), which send a periodic update every 30 and 90 seconds, respectively, use valuable bandwidth to maintain a table without summarization. RIP can fit 25 networks in each update; therefore, 10,000 networks can have RIP on every router creating and sending 400 packets every 30 seconds. When these routes summarize, the table of 249 networks sends only 10 packets every 30 seconds, compared to the 400 packets from the unsummarized routing table.

Unsummarized Internetwork Topology Changes A routing table with 10,000 entries constantly changes. To illustrate this constant change, consider a network that has more than 5000 routers, with at least one at 5000 different sites. Something changes somewhere in the network every day, for example, a power outage occurs at site A; a backhoe digs a trench at site B; a newly hired system administrator begins work at site C; a Cisco IOS software upgrade is in progress at site D; and a newly added router is being installed at site E. There are other examples of this negative impact as well. For example, when you are using a routing protocol such as Open Shortest Path First (OSPF), an upgrade or topology change on the internetwork causes a shortest path first (SPF) calculation. The SPF calculations are large, because each router needs to calculate all known pathways to each of the 10,000 networks. Each change that a router receives requires time and CPU resources.

Copyright © 2005, Cisco Systems, Inc. Advanced IP Addressin