- Paperback: 688 pages
- Publisher: Addison-Wesley; 1st edition (December 21, 2000)
- Language: English
- ISBN-10: 9780201704556
- ISBN-13: 978-0201704556
- ASIN: 0201704552
- Product Dimensions: 7 x 1 x 8.8 inches
- Shipping Weight: 2.2 pounds
- Average Customer Review: 7 customer reviews
- Amazon Best Sellers Rank: #5,154,877 in Books (See Top 100 in Books)
Enter your mobile number or email address below and we'll send you a link to download the free Kindle App. Then you can start reading Kindle books on your smartphone, tablet, or computer - no Kindle device required.
To get the free app, enter your mobile phone number.
High Availability Networking with Cisco Paperback – December 21, 2000
From the Inside Flap
This book explores and discusses a wide range of potential approaches to improving network availability, allowing you to choose those most appropriate for your organization and its unique needs and constraints. The goal is to show how to achieve higher network availability both in theory and in practice. In economic terms, this means pushing the design to the point where the cost of eliminating further unavailability exceeds the cost to the organization of the losses due to downtime.
While the theoretical aspects apply to networks of all sizes and technologies, the example solutions provided focus on the needs of moderate sized extended corporate networks using IP version 4 and stable, moderate performance technologies such as frame relay, ISDN, and Ethernet--not because these technologies are fundamentally more or less reliable than others, but because these tend to be the networks which have grown to the point of being critical to the day-to-day operations of the organization without a staff of dedicated network designers and architects to provide optimization and support. How to Use This Book
This book is written for those looking for design techniques to cost effectively improve network availability. The reader is assumed to be knowledgeable in the fundamentals of large network design and comfortable going to other references for more details on specific protocols and functions.
The basic approach of this book is divide and conquer. Each chapter attacks a general need of high availability network design, from defining what high availability really means and requires in the first chapter to the final chapter's discussion of the essential commitment to a full range of network management capabilities. Within each chapter, the general need is broken down into specific requirements. Within each specific requirement, the problem being addressed and possible solutions are first discussed on a general theoretical level. Wherever practical, one or more specific scenarios are defined and example solutions implemented, typically using Cisco routers.
Please read through the example implementations even if you never expect to touch a Cisco system. The examples and their accompanying discussions serve to flesh out the theoretical framework, showing typical adjustments required to get the theory presented to actually work in a real world environment. Many of these adjustments have nothing to do with Cisco, but rather reflect limitations in the current implementations of network protocols.
Technical managers and others will find this book's survey of all aspects of high availability network design invaluable. There are a vast array of considerations which should be part of any design and tunnel vision can be costly. It is very easy (and common) to implement point solutions which in the process of eliminating one weakness introduce other modes of failure. Choosing the best solution is rarely possible without a system-wide perspective.
Network implementors in a Cisco environment will find this book a cookbook of Cisco solutions that they can modify and install in their own network. These readers should still pay attention to the theoretical discussions preceding each example so they can identify modifications necessary to fit their unique environment.
It is essential for all to keep in mind that high availability is not just a design parameter, it is also an executive management commitment to funding adequate resources, staffing and training for the life of the network. At the same time, even though this book focuses on enhancing the availability of the network, we must always keep our sense of perspective. From the user's viewpoint, it is immaterial whether it is the network, the server, the software or the client platform which fails. Cost effective availability improvement needs to be balanced across all causes of failure to ensure that the resources required are applied where they will have the most impact on the bottom line.
This is much easier to say than it is to do, as few organizations even know what their current availability is or keep any statistics on the causes of failure. Even fewer organizations have proceeded to the stage of analyzing their bottom line costs for various failure modes. But higher network availability remains indisputably important. Fortunately, it is never too late to start on the road to higher availability. Chapter by Chapter
Chapter 1, "Reliability and Availability," introduces the theory and technology of high availability networks. First the stage is set with the potential cost of network downtime for mundane production as well as ''must run'' networks. The mathematical basis behind predicting availability, different approaches to providing higher availability, and the availability challenges unique to computer networks form the core of the chapter. The chapter ends with the need to provide physical diversity in multiply connected WANs and LANs, setting the stage for the rest of the book.
High availability is not an automatic result of adding redundant links and components to a network. Adding redundancy adds complexity to the network, which must be recognized and utilized. Chapter 2,"Bridging and Routing," starts out with a quick review of network terminology, then surveys the available layer two bridging approaches (simple learning, SR and TST) and popular layer three routing protocols for IP (static, RIP, OSPF, Integrated IS-IS, EIGRP and BGP), briefly discussing how each works and the strengths and weaknesses of each. Along the way, parameter tuning which may be appropriate to speed up response to failures is explored and examples provided.
Chapter 3, "Multihomed Hosts," extends the availability benefits of redundant connectivity all the way to the end system in an IP network. Starting with the simple step of adding a second NIC to an end system, the challenges presented in supporting applications when the server (or client) has two IP addresses are explored. Then two approaches to giving the two NICs the appearance of a single IP address (proprietary and via routing) are examined, with full configuration examples for the latter. The chapter concludes with a discussion of server cluster terminology, techniques and limitations.
Dial backup is a popular alternative to installing additional ''permanent'' links. In Chapter 4, "Dial Backup for Permanent Links," the first of two dedicated to dial backup, three different dial backup approaches are introduced, distinguished by how the router determines the need to place a call. After exploring the underlying assumptions behind each and how those assumptions affect their suitability for various applications, a basic ''how to'' for IP dial backup is provided. Using examples of ISDN dial backup applied to leased lines, frame relay, and DSL, the critical factors requisite to successful implementation are highlighted.
Chapter 5, "Advanced Dial Backup," extends the general concepts introduced in chapter 4 to meet the specific needs of a range of requirements. It starts with the challenge of using asynchronous modems rather than ISDN, then moves on to explore techniques for combining multiple dial links to provide higher bandwidth. After a brief look at providing IPX support, the chapter concludes with how to use BGP with generic dial-on-demand routing to provide dial backup driven by routing table changes without the limitations associated with Cisco's proprietary dialer watch facility.
Chapter 6, "Multiple Routers at a Single Site," focuses on eliminating the router as a single point of failure from the viewpoint of preventing end-systems at a location from being isolated from the rest of the WAN. Starting with solutions to the limitations inherent in the IP concept of a default gateway, the chapter then explores how to provide a second router without doubling the WAN communications costs by getting one router to provide dial backup for a link on another router. It then finishes with how to configure the routers on a physically extended LAN so that even if the LAN is split in two by a failure, IP systems on both halves of the LAN can still communicate with the outside world.
Chapter 7, "Hub and Spokes Topology," explores the unique requirements of hub and spokes networks. Hub and spokes is a popular topology for HQ data center and other applications because it allows major simplifications in the routing structure, but it can also introduce complications. The chapter starts with a discussion on how to get around limitations on the number of peers supportable on a single router and how to scale a hub and spokes design to handle an arbitrary number of spokes without requiring the spoke routers to maintain more than a handful of routes each. The focus then shifts to configuring dial-on-demand routing so that a spoke router can dial any of several routers at the hub without concern for which answers. Finally, critical considerations when the hub expands to actually be multiple sites, such as a primary and backup data center, are explored.
Chapter 8, "Connecting to Service Provide
From the Back Cover
Keeping a network continuously available despite the many potential hazards that can shut it down is a job that network implementors and technical managers struggle with every day. High Availability Networking with Cisco shows those charged with that increasingly important task how to achieve higher network availability both in theory and in practice. Using a "divide-and-conquer" approach, each chapter dissects the general need of high availability network design. The specific challenges and available solutions for each need are first discussed on a theoretical level. When appropriate, one or more implementation examples are presented, showing how the theory translates into working Cisco router configurations.
Although the examples use Cisco routers, the underlying theory is vendor-independent, and most of the solutions presented easily can be adapted to routers and switches from any vendor. Similarly, the theoretical aspects discussed in this book can be applied to networks of all sizes and technologies. Sample solutions focus on the needs of moderately sized extended corporate networks using IP version 4.0 and stable performance technologies such as frame relay, ISDN, and Ethernet.
Readers will find an invaluable survey of all aspects of high availability network design, including the following:
- Network vulnerabilities and appropriate counter measures
- Selecting and tuning bridging and routing protocols for higher availability
- Multihomed hosts from individual client-to-server clusters
- Dial backup over asynchronous and ISDN links
- Single points of failure despite multiple routers at a single site
- Hub and spokes design approaches that scale
- Linking to another private network
- Multiple links to one or more Internet service providers
- Alternate routing through redundant firewalls without sacrificing security
- Supporting legacy systems using Data Link Switching (DLSw)
- Disaster-recovery options, including hot backup and load sharing approaches
- Management considerations ranging from status monitoring to total quality control
By using many examples drawn from working configurations proven to be successful in actual corporate networks, High Availability Networking with Cisco reflects the author's extensive experience helping clients minimize the impact of failure on network operations
Showing 1-4 of 7 reviews
There was a problem filtering reviews right now. Please try again later.
The first chapter defines the concept of network availability and introduces some of the elementary mathematical tools needed to characterize it. The author stresses the need for performing a 'availability management analysis' to measure the current availability of a network and study the causes of past failures. He also points out the "catch-22s" in the naive application of availability analysis, such as the need for insuring no common failure modes when employing parallel redundancy.
Chapter two discusses bridging and routing, with careful attention given to the designations of "switch" and "hub", and to the choice of network topology. The routing protocols RIPv2, OSPF, EIGRP, integrated IS-IS, and BGP are discussed in terms of their stability, performance and availability. Explicit calculations for the metric in EIGRP are given, to illustrate the difference between it and OSPF when redundancy is present.
In chapter 3, the author considers various approaches that allow the network engineer to extend the multiply-connected design of the HA network to the network end systems. This will have the effect of eliminating all single points of failure associated with network access. He first considers the incorporation of a second network interface with independent addresses and the problems that could arise in this approach, these having to do with the network protocol architecture used, the routing protocols in place on the two interfaces, and the application recovery requirements.
The use of redundant routers to ensure network availability is discussed in Chapter 6. Although it is simple to implement this redundancy, the author cautions the reader that it is the other components in the network that cause problems when using redundant routers. Crucial in these considerations is the providing of router independence for the end systems, and the author reviews several protocols for doing this, including passive RIP, proxy ARP, IRDP, DHCP, VRRP, and of course Cisco HSRP. The latter has proved its mettle in allowing transparency to the end systems, load balancing, and the prevention of routing black holes, but the author also stresses that care must be taken to ensure that efficiency is preserved and awareness must be made of the hardware limitations of the routers using HSRP. A very detailed discussion is given on how to protect against LAN segmentation. A real-world example is given that illustrates all of the concepts that the author discusses in this chapter.
Networks built on the hub-and-spoke topology are discussed in chapter 7. Such topologies are usually the result of legacy designs in enterprise businesses and evolve into more hierarchical tree topologies as the business grows. The author's goal in this chapter is to study to what extent the connectivity and fault tolerance of these kinds of network architectures can be improved. The proper routing protocols to use for these kind of topologies are discussed first, and, because of the HA requirement, must be chosen to be dynamic, despite the belief to the contrary that static routes would be sufficient for such simple network topologies. EIGRP is considered to be the routing protocol of choice in these kinds of topologies, and the author discusses in detail why this is the case.
The author directs his attention to the issues involved in HA when using Internet Service Providers with the discussion limited to the TCP/IP protocol. BGP is the protocol of choice here, due to the proliferation of routing domains in the Internet, and security issues are much more sensitive in such environments, as the author shows in great detail. In particular, an example is given of using network address translation to route return traffic. The author also discusses the case where there is a connection to two independent ISPs, providing redundancy to the system on the other side of the Internet. Although total Internet failures are relatively rare, their duration is usually long enough to entail a serious loss of revenue to businesses that depend on the Internet predominantly for this revenue. The author discusses several issues that arise in connecting through multiple ISPs, such as address space, since there are three different classes of public Internet addresses. The interdomain routing with Border Gateway Protocol entails the participation in routing over the Internet as an independent Autonomous System. This guarantees reachability from any other end system that has a path to any of the ISPs used.
In chapter 9, the author addresses availability issues when connecting through firewalls. The security reasons for the deployment of firewalls do not totally dominate the chapter. The author also discusses how the properties of firewalls affect the network design. He emphasizes that the goal in using firewalls is to ensure that the path through them is state sensitive and it must be known as to when they will appear to a router as an end-system or simply as another router. He explains using examples how these distinctions impact network design, and cautions that considerations of router mode versus end-system mode should not be confused with proxy-mode versus pass-through mode considerations. Also discussed are firewalls in a fully redundant network, and the high availability requirements dictate that even greater attention be paid to security issues, since breaches of security may prevent the availability goals. Examples of redundant firewalls with hot standby failover and with load sharing failover are also discussed in detail. The conflict between the needs of routing and the security requirements of firewalls is readily apparent throughout this chapter.
I am not going to rehash the table of contents or the lengthly editorial review - I am going to jump into why I like this book and what I think makes it so valuable.
First, no 24x7 system is a true highly available information resource unless you can access it. Try as I may, I cannot think of a single company that does not employ a network as the base infrastructure for their information systems. This book provides information necessary to create a foundation for high-availability and 24x7 operations.
Second, the book is a catalog of high availability designs that will fit within any network architecture, regardless of complexity, products used or geographical scope. No matter what your network currently looks like you will find out what it takes to transform it into a reliable, resilient 24x7 network. The author has provided a design strategy for every conceivable situation and network configuration, and thoroughly discusses the underlying technical issues. This is where the "Cisco" part of the title comes in - he uses that particular product family as examples for achieving high availability designs for each scenario.
Third, the disaster recovery section in the book is well thought out and shows that the author has a lot of knowledge and experience in business continuity planning and disaster recovery. This section alone is worth the price of the book.
This book is, in my opinion, essential reading for network architects, consultants and integrators, and operations managers who are seeking a total solution to high-availability solutions.
What I would love to see is a follow-on book that provides the design information reformatted as design patterns. This would be an invaluable resource for experienced network architects and consultants.
This book is a must-have reference for wide area networking engineers. The book provides both background and practical configuration advice for a wide range of WAN scenarios. What makes this book uniquely helpful is the way that the author steps through each of the available Cisco techniques for providing redundancy. The author first explains how the technology works, and then proceeds to show full example configurations, and then explains real world caveats of the configuration. Reading this book gave me a clear understanding of the different types of fail-over and redundancy available in Cisco products, and in which circumstances each would be most applicable.
I would recommend that anyone designing a WAN read this book cover to cover and then keep it as a reference for future design work. I've read it multiple times already and with each new project I find another section that applies directly to my work.