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Troubleshooting OpenVPN

Book Description

Get the solutions you need to troubleshoot any issue you may face to keep your OpenVPN up and running

About This Book

  • This is the first book on the market that resolves your issues related to troubleshooting OpenVPN
  • Ensure your organization's private network is protected 24x7 by resolving OpenVPN issues instantly
  • Save time and costs by troubleshooting to reduce the impact on your business

Who This Book Is For

The book is for system administrators who are experienced and well versed with OpenVPN. You should possess intermediate to master level proficiency with OpenVPN. All OpenVPN users can leverage this book.

What You Will Learn

  • Diagnose and remediate authentication and authorization problems in OpenVPN
  • Overcome simple network and startup script errors
  • Learn OpenVPN log file format and verbosity options
  • Resolve operating system-specific errors
  • Discover various troubleshooting techniques to resolve problems in OpenVPN
  • Improve performance and identify bottlenecks in the network or with hardware
  • Determine external versus internal network issues

In Detail

OpenVPN, the most widely used open source VPN package, allows you to create a secure network across systems, keeping your private data secure. Connectivity and other issues are a pain to deal with, especially if they are impacting your business. This book will help you resolve the issues faced by OpenVPN users and teach the techniques on how to troubleshoot it like a true expert. This book is a one stop solution for troubleshooting any issue related to OpenVPN.

We will start by introducing you to troubleshooting techniques such as Packet Sniffing, Log Parsing, and OpenSSL. You will see how to overcome operating system specific errors. Later on, you will get to know about network and routing errors by exploring the concepts of IPv4 and IPv6 networking issues. You will discover how to overcome these issues to improve the performance of your OpenVPN deployment.

By the end of the book, you will know the best practices, tips, and tricks to ensure the smooth running of your OpenVPN.

Style and approach

This is a practical and straight-to-the point book that troubleshoots all the issues related to OpenVPN and provides best practices, tips, and tricks.

Downloading the example code for this book. You can download the example code files for all Packt books you have purchased from your account at http://www.PacktPub.com. If you purchased this book elsewhere, you can visit http://www.PacktPub.com/support and register to have the code file.

Table of Contents

  1. Troubleshooting OpenVPN
    1. Troubleshooting OpenVPN
    2. Credits
    3. About the Author
    4. About the Reviewer
    5. www.PacktPub.com
      1. Why subscribe?
    6. Customer Feedback
    7. Preface
      1. What this book covers
      2. What you need for this book
      3. Who this book is for
      4. Conventions
      5. Reader feedback
      6. Customer support
        1. Errata
        2. Piracy
        3. Questions
    8. 1. Troubleshooting Basics
      1. A recommended toolkit
        1. Log search and filtering
          1. grep
          2. less, more, and most
          3. Regular expressions
        2. Network sniffing and analysis
          1. tcpdump
          2. traceroute
          3. mtr
          4. ping
          5. Wireshark
        3. X.509 verification and inspection
          1. OpenSSL
          2. Wireshark
      2. Troubleshooting basics
      3. Summary
    9. 2. Common Problems
      1. Narrowing the focus
        1. Sample scenarios
          1. Scenario 1--unable to access VPN
          2. Scenario 2--cannot access external web when on VPN
        2. Suspecting recent changes
      2. Supported operating systems
        1. Embedded devices
        2. Semi-embedded systems
        3. Virtual servers
      3. IP addresses
      4. Firewalls
      5. Duplicate client certificates
      6. Overcomplication
      7. Summary
    10. 3. Installing OpenVPN
      1. Common installation problems
        1. Compiling OpenVPN
        2. Packages and installers
          1. The advantages of precompiled installers
        3. Driver installation
      2. Alternative clients
      3. Summary
    11. 4. The Log File
      1. Logging options
      2. Logging levels
        1. Verbosity 0
        2. Verbosity 1
        3. Verbosity 4
        4. Verbosity 7
      3. Common log messages
        1. Startup messages
          1. Version and compile string
          2. Option warnings
          3. Configuration parameters
        2. Operational messages
          1. Certificate messages
      4. Summary
    12. 5. Client and Server Startup
      1. File and process permissions
        1. Privilege de-escalation
        2. Networking privileges
          1. Port assignment and use
            1. Multiple daemons
          2. Adapter and routing table changes
        3. Chroot
      2. Scripting
        1. Up and down scripts
        2. Connect and disconnect scripts
      3. UDP troubleshooting
        1. UDP and firewalls
      4. Summary
    13. 6. Certificates and Authentication
      1. File permissions
      2. Pre-shared keys
      3. Certificate authentication
        1. Certificate chain overview
        2. The Certificate Revocation List
        3. System date and time
      4. Authentication and plugins
        1. Usernames and passwords
        2. --ccd-exclusive
      5. Summary
    14. 7. Network and Routing
      1. Connectivity
        1. Inbound connection--server
          1. Publicly addressed server
          2. Privately addressed server with port forwarding
        2. Outbound connection--client
      2. Firewall filters and inspection
      3. TLS authentication
      4. Routing
        1. Internal routing
        2. External routing
        3. Pushing routes
          1. Routes behind clients
          2. Kernel versus process routing
          3. Route conflicts
        4. Redirect gateway
      5. General network concerns
        1. Path MTU and MSS
      6. Summary
    15. 8. Performance
      1. Networking
        1. Rate limiting
      2. Cryptographic performance
        1. Library differences
        2. Cipher and AES-NI
        3. Result summary
      3. Single thread
      4. Summary
    16. 9. External Problems
      1. Inspection and filtering
        1. Obfuscation
        2. Encryption
        3. Geographic and source address exclusions
          1. What can be done
            1. Source IP address
            2. DNS settings
      2. Routing path performance
      3. Summary
        1. Useful links
          1. Manual or man pages
          2. Release notes
          3. Support channels