The Organization of This Book

This book is based on the premise that if you really want to troubleshoot, you need to go through some preliminary phases first. You need to start with the technology basics, progress through design and configuration solutions, and finally get to the troubleshooting methodologies, techniques, and tools. Every chapter of this book is organized according to this concept, and every chapter includes review questions. Finally, the examples and the scenarios in Parts II, III, IV, and V are live-based and represent the best proven practices from more than tens of thousands of cases handled by the Cisco Remote Access team.

Part I: Remote Access Fundamentals

Part I, which describes the fundamentals of remote access networks, is the technological foundation of this book. This part includes management considerations and remote access service options. It provides relatively extensive information about telecommunications basics, modulations, and coding techniques in wired, wireless, and hybrid environments. An integral part of this discussion is the clocking, line coding, and framing in carrier systems, including the most common T1s and PRIs. An important section of Part I is the discussion about the cloud, and how the carriers and service providers handle the traffic. The information about the future of the service and the last-mile initiative of Cisco is provided as well.

Although the first three chapters are about the remote access environment, the last chapter in Part I is about remote access inter-network layered models, methodology, and tools. In this chapter, the layer-by-layer model of troubleshooting is introduced as one systematic approach to troubleshooting issues.

Part II: Dial

Part II is devoted to one of the most traditional remote access technologies: dial networking. The initial technology information is designated to underline some of the fundamentals and specifics of dial, in addition to the information provided in Part I. The detailed description of modems and the overview of possible provider issues, as well as the detailed description of Point-to-Point Protocol (PPP), is among the main topics covered. The design chapter includes information about text dialin network, PPP dialin network, text dial-out network, PPP dial-out network, large scale dial-out network, and dial-on-demand backup network, all of which are well-known design solutions in the industry today. The same set of design solutions is also presented from a configuration point of view, with the necessary explanations, tips, and notes. The dial troubleshooting section includes information on troubleshooting T1 and PRI circuits, dialin service, dial-out service, and important access server (AS5x00) specific commands and debugs.

The troubleshooting scenario chapter focuses on authentication problems, frequent retrains and disconnects, and dirty phone lines and bad modems.

Part III: ISDN>

Part III is about Integrated Services Digital Network (ISDN)especially ISDN BRI. This part provides concise ISDN technology background information about standards, channels, and ISDN architecture. The necessary troubleshooting information about reference points, interfaces, and initializing of layers one, two, and three is provided here, as is information about ISDN switch types. The common ISDN design solutions are focused on NAT/PAT configurations and virtual profiles and interfaces. Separate sections are designated to provide detailed discussion about Multilink Point-to-Point Protocol (MP) and Multi-Chassis Multilink Point-to-Point Protocol (MMP) designs. The configuration chapter focuses on ISDN cost-effective solutions, such as spoofing, snapshot routing, and dial-on-demand routing (DDR). The ISDN troubleshooting chapter illustrates the layer-by-layer approach and includes detailed discussion about each and every layer, as well as extended information about troubleshooting MP, MMP, and telephone interfaces.

The troubleshooting scenarios include new install problems, dial-out problems, performance issues, end-to-end problems, and Windows 2000 and Cisco DDR controversy.

Part IV: Frame Relay

The main focus of Part IV is Frame Relay. More information is provided about the end user's side of the design than about the corporate side. The Frame Relay standards, protocols, and service architecture are the main foundation topics. The Frame Relay design provides detailed information about User-Network Interface (UNI) and Network-to-Network Interface (NNI). Frame Relay performance criteria, fragmentations, Inverse ARP, upper-layer protocols, and Local Management Interface (LMI) are among the design objectives of Part IV. The Frame Relay configuration provides some common configuration solutions and explanations. The advanced configuration section includes IP unnumbered solution, frame switching, Frame Relay backup, compression, multicast, and traffic shaping. The Frame Relay troubleshooting chapter applies the layer-by-layer approach and discusses Layer 1 and 2 problems, performance, end-to-end issues, compression, and traffic-shaping problems.

The Frame Relay troubleshooting scenarios in Chapter 18 focus on new installs, wrong DLCI, LMI settings, and performance and multicast issues. Rehosting of Frame Relay service is included as well.

Part V: VPN

Virtual Private Network (VPN) is about running private data over public networks. Part V provides the minimum initial background for all versions of VPN, but focuses on remote access solutions. PPTP, L2TP, IPSec, and key agreements are discussed in detail. The common design solutions, the termination points, software and hardware VPN clients, EzVPN, and PIX-based solutions are explained concisely. All available remote access VPN solutions and their configurations are another important part here. They include Cisco VPN 3000 Series Concentrator configuration and Cisco VPN client configuration (including Cisco Unity VPN Client, Cisco VPN 3002 HW Client, Cisco Easy VPN IOS, and Cisco PIX 501 and 506 Client). The VPN troubleshooting chapter includes extensive and detailed explanations, divided into three main groups: Cisco VPN client issues, VPN and Internet technologies issues, and VPN and LAN issues affecting remote access VPN.

The scenarios in Chapter 22 include VPN over PPPOE, authentication problems and cannot pass data issues, hardware VPN client issues, and extranet issues.