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Optimal Routing Design

Book Description

Techniques for optimizing large-scale IP routing operation and managing network growth 

  • Understand the goals of scalable network design, including tradeoffs between network scaling, convergence speed, and resiliency

  • Learn basic techniques applicable to any network design, including hierarchy, addressing, summarization, and information hiding

  • Examine the deployment and operation of EIGRP, OSPF, and IS-IS protocols on large-scale networks

  • Understand when and how to use a BGP core in a large-scale network and how to use BGP to connect to external networks

  • Apply high availability and fast convergence to achieve 99.999 percent, or “five 9s” network uptime

  • Secure routing systems with the latest routing protocol security best practices

  • Understand the various techniques used for carrying routing information through a VPN

  • Optimal Routing Design provides the tools and techniques, learned through years of experience with network design and deployment, to build a large-scale or scalable IP-routed network. The book takes an easy-to-read approach that is accessible to novice network designers while presenting invaluable, hard-to-find insight that appeals to more advanced-level professionals as well.

    Written by experts in the design and deployment of routing protocols, Optimal Routing Design leverages the authors’ extensive experience with thousands of customer cases and network designs. Boiling down years of experience into best practices for building scalable networks, this book presents valuable information on the most common problems network operators face when seeking to turn best effort IP networks into networks that can support Public Switched Telephone Network (PSTN)-type availability and reliability.

    Beginning with an overview of design fundamentals, the authors discuss the tradeoffs between various competing points of network design, the concepts of hierarchical network design, redistribution, and addressing and summarization. This first part provides specific techniques, usable in all routing protocols, to work around real-world problems. The next part of the book details specific information on deploying each interior gateway protocol (IGP)–including EIGRP, OSPF, and IS-IS–in real-world network environments. Part III covers advanced topics in network design, including border gateway protocol (BGP), high-availability, routing protocol security, and virtual private networks (VPN). Appendixes cover the fundamentals of each routing protocol discussed in the book; include a checklist of questions and design goals that provides network engineers with a useful tool when evaluating a network design; and compare routing protocols strengths and weaknesses to help you decide when to choose one protocol over another or when to switch between protocols.

    “The complexity associated with overlaying voice and video onto an IP network involves thinking through latency, jitter, availability, and recovery issues. This text offers keen insights into the fundamentals of network architecture for these converged environments.”

    –John Cavanaugh, Distinguished Services Engineer, Cisco Systems®

    This book is part of the Networking Technology Series from Cisco Press‚ which offers networking professionals valuable information for constructing efficient networks, understanding new technologies, and building successful careers.

    Table of Contents

    1. About This eBook
    2. Title Page
    3. Copyright Page
    4. About the Authors
    5. About the Technical Reviewers
    6. Dedications
    7. Acknowledgments
    8. Contents at a Glance
    9. Contents
    10. Icons Used in This Book
    11. Command Syntax Conventions
    12. Foreword
    13. Introduction
      1. Who Should Read This Book?
      2. How This Book Is Organized
      3. Final Words
    14. Part I: Network Design Overview
      1. Chapter 1. Network Design Goals and Techniques
        1. Goals for Network Design
        2. Reliability
          1. Packet Delivery Reliability
          2. Packet Delivery Times
          3. Delay and Jitter Budgets
          4. The Impact of Network Design on Delay and Jitter Budgets
        3. Reliability and Resiliency
          1. Defining Network Failure
          2. Network Recovery Time
        4. Manageability
          1. Day-to-Day Operational Maintenance
          2. Emergency Management
        5. Scalability
          1. Redundancy
        6. Layering
          1. Hiding Information
          2. Separate Functionality
        7. Summary
        8. Review Questions
      2. Chapter 2. Applying the Fundamentals
        1. Hierarchical Design
          1. Abstraction Through Layering
          2. Horizontal Layers in a Network
          3. Layer Functions
          4. Network Hierarchies
        2. Addressing and Summarization
          1. Assigning Addresses in a Network
          2. Working Around Addressing
          3. Summary Issues
        3. Redistribution
          1. Alternatives to IGP to IGP Redistribution
          2. Single Point of Redistribution
          3. Multiple Points of Redistribution
        4. Review Questions
    15. Part II: Interior Gateway Protocols
      1. Chapter 3. EIGRP Network Design
        1. Deploying EIGRP on a Large-Scale Three-Layer Hierarchical Network
          1. Analyzing the Network Core for Summarization
          2. Analyzing the Network Distribution Layer for Summarization
          3. Analyzing Routing in the Network Access Layer
          4. Analyzing Use of the Stub Feature in Access Routers
          5. Analyzing Routes to External Connections
          6. Analyzing Routes to the Common Services Area
          7. Analyzing Routes to Dial-In Clients
        2. Deploying EIGRP on a Two-Layer Hierarchical Network
          1. Summarization in the Core
          2. Summarization in the Aggregation Layer
          3. Summary of EIGRP Network Design
        3. New Features in EIGRP
          1. Third-Party Next Hop
          2. Enhanced Route Map Support
          3. Enhanced EIGRP Active Process
        4. Case Study: Summarization Methods
          1. IP Summary Addresses
          2. Distribute Lists
        5. Case Study: Controlling Query Propagation
        6. Case Study: A Plethora of Topology Table Entries
        7. Case Study: Troubleshooting EIGRP Neighbor Relationships
          1. EIGRP Neighbor Relationships: Common Problem 1
          2. EIGRP Neighbor Relationships: Common Problem 2
        8. Case Study: Troubleshooting SIA Routes
        9. Case Study: Redistribution
          1. Using Distribute Lists to Prevent Redistribution Routing Loops
          2. Using Route Maps to Prevent Redistribution Routing Loops
          3. Using Prefix Lists to Prevent Redistribution Routing Loops
          4. Setting the Administrative Distance to Troubleshoot Redistribution Routing Loops
          5. Using External Flags to Prevent Redistribution Routing Loops
        10. Case Study: Retransmissions and SIA
          1. The Hold Timer
          2. SIA Timer
          3. Interaction Between the Hold Timer and the SIA Timer
        11. Case Study: Multiple EIGRP Autonomous Systems
        12. Review Questions
      2. Chapter 4. OSPF Network Design
        1. Summarization and Aggregation
          1. Deploying OSPF on a Three-Layer Hierarchy
          2. Deploying OSPF on a Two-Layer Hierarchy
          3. Reducing Flooding Through Stub Areas
          4. Aggregating Routes in OSPF
          5. Filtering Routes in OSPF
        2. Deploying OSPF on Specific Topologies
          1. Redistribution into OSPF
          2. Full Mesh Topologies
          3. Hub-and-Spoke Topologies
          4. Links Parallel to Area Boundaries
          5. Dial Links
          6. Point-to-point Broadcast Links
        3. Case Study: OSPF Externals and the Next Hop
        4. Case Study: Troubleshooting OSPF Neighbor Adjacencies
        5. Review Questions
      3. Chapter 5. IS-IS Network Design
        1. Deploying IS-IS on a Three-Layer Hierarchy
          1. The Entire Network as a Single Routing Domain
          2. The Core as the L2 Domain
          3. Merging the Core and Distribution Layers into Level 2
          4. Mixing and Overlapping the Level 1/Level 2 Border
        2. Deploying IS-IS on a Two-Layer Hierarchy
        3. Working with IS-IS Routing Areas
          1. Leaking Routes into an L1 Routing Domain
          2. Aggregating Routes in IS-IS
        4. Deploying IS-IS on Specific Topologies
          1. Redistribution
          2. Full Mesh Topologies
          3. Hub-and-Spoke Topologies
          4. Point-to-Point Broadcast Links
          5. Links Parallel to Area Boundaries
        5. Other Considerations in IS-IS Scaling
          1. Metrics
          2. Excessive Link-State Flooding
          3. LSP Corruption
          4. Maximum Number of Pseudonodes
          5. Prefix-Driven Routing Table Installation
          6. Hello Padding Suppression
        6. Case Study: Troubleshooting IS-IS Neighbor Relationships
        7. Review Questions
    16. Part III: Advanced Network Design
      1. Chapter 6. BGP Cores and Network Scalability
        1. Case Study: Troubleshooting BGP Neighbor Relationships
          1. No IP Connectivity
          2. eBGP Multihop
          3. Other BGP Neighbor Problems
          4. Logging Neighbor Changes
        2. BGP in the Core
          1. Case Study: Sample Migration
        3. Scaling Beyond the Core
          1. Dividing the Network into Pieces
          2. Regional IGPs
        4. BGP Network Growing Pains
          1. BGP Update Generation Issues
          2. Case Study: Route Reflectors as Route Servers
        5. External Connections
          1. Case Study: Dual-Homed Connections to the Internet
          2. Case Study: Conditional Advertisement
          3. Case Study: Route Dampening
        6. Review Questions
      2. Chapter 7. High Availability and Fast Convergence
        1. Considerations in Fast Convergence
          1. Network Meltdowns
          2. Solving the Meltdown
          3. Designing Routing Protocols Not to Melt
          4. Do Not Report Everything You See
          5. Non-Stop Forwarding
          6. Graceful Restart
        2. Fast Down Detection
          1. Detecting a Link or Adjacency Failure Using Polling
          2. Detecting a Link or Adjacency Failure Using Event-Driven Link Failure Notification
        3. Slowing Down When the Network Speeds Up
          1. Link-State Exponential Backoff
          2. IP Event Dampening
        4. Calculating the Route Faster
          1. EIGRP Feasible Successors
          2. Link-State Partial SPF
          3. Link-State Incremental SPF
        5. Deploying GR and Fast Convergence Technologies
          1. Graceful Restart Versus Fast Down Detection
          2. Deploying Graceful Restart with BGP and an Interior Gateway Protocol (IGP)
          3. Deploying Exponential Backoff for Fast Convergence
        6. Review Questions
      3. Chapter 8. Routing Protocol Security
        1. Fundamentals of Routing and Security
          1. Understanding What a Routing System Is
          2. Thoughts on Authorization and Authentication
          3. Determining the Reasons for an Attack on the Routing System
        2. Types of Attacks Against Routing Systems
          1. Disrupting Peering
          2. Falsifying Routing Information
          3. Disrupting Routing Domain Stability
        3. Protecting Routing Domain Legitimacy
          1. Protecting Routers from Being Compromised
          2. Protecting Against Illegitimate Devices Joining the Routing Domain
          3. Protecting Routers from Denial-of-Service Attacks
        4. Protecting Routing Information
          1. Extranet Connections
          2. Connections to the Internet
        5. Future Directions in Routing Protocol Security
          1. Protecting Against Illegitimate Devices Joining the Routing Domain
          2. Secure Origin BGP (soBGP)
        6. Review Questions
        7. References
      4. Chapter 9. Virtual Private Networks
        1. MPLS
          1. MPLS Basics
          2. Overlay Routing over MPLS VPNs
          3. Peer-to-Peer (Redistributed) Routing over MPLS VPNs
          4. BGP/MPLS VPNs
        2. IPSec
        3. GRE
        4. NHRP
          1. Case Study: NHRP in an ATM Network
        5. Dynamic Multipoint IPSec VPNs
        6. Review Questions
        7. References
    17. Part IV: Appendixes
      1. Appendix A. EIGRP for IP Basics of Operation
        1. DUAL
        2. Neighbor Relationships
        3. Metrics
        4. Loop-Free Routes
          1. Clearing the Topology Table and Querying Neighbors
        5. SIA
        6. Bounding Queries
          1. Summarization
          2. Stub Routing
        7. Using the Metrics
          1. Load Balancing
      2. Appendix B. OSPF Basics of Operation
        1. General Theory of OSPF
          1. Router IDs
          2. LSAs
          3. LSA Age
          4. Reliable Flooding of LSAs
          5. Building Adjacencies
          6. Adjacencies on Multiaccess Networks
          7. Areas
        2. External Route Injection
        3. Virtual Links
      3. Appendix C. Integrated IS-IS Basics of Operation
        1. General Theory
        2. CLNS Addressing
        3. Routing
        4. Metrics
        5. Building Adjacencies
        6. LSP Flooding and SPF Recalculation Timers
        7. Neighbor Loss and LSP Regeneration
        8. IP Integration into IS-IS
        9. Multiple net Statements
      4. Appendix D. Border Gateway Protocol 4 Basics of Operation
        1. A Path Vector Protocol
        2. Path Decision
          1. Administrative Weight
          2. Local Preference
          3. AS Path Length
          4. MED
          5. Lowest Router ID
          6. Community
        3. Operation
          1. Exterior BGP
          2. Interior BGP
        4. The Next Hop Attribute
          1. Filtering
          2. Route Maps
          3. Prefix Lists
          4. Distribution Lists
          5. Synchronization
          6. Summarization
      5. Appendix E. IP Network Design Checklist
        1. Basic Network Operations Questions
        2. Topological Layout
        3. Redistribution and Interconnection
        4. Security
      6. Appendix F. Answers to Review Questions
        1. Chapter 1
        2. Chapter 2
        3. Chapter 3
        4. Chapter 4
        5. Chapter 5
        6. Chapter 6
        7. Chapter 7
        8. Chapter 8
        9. Chapter 9
      7. Appendix G. Which Routing Protocol?
        1. Is One Protocol “Better” Than the Others?
        2. Ease of Troubleshooting
        3. Which Protocol Converges Faster?
        4. Which Designs Play to the Strength of Each Protocol?
          1. Hub-and-Spoke Topologies
          2. Full Mesh Topologies
          3. Interaction with Hierarchical Designs
          4. Topological Rules of Thumb
        5. What Are the Tradeoffs?
    18. Index
    19. Code Snippets