Chapter 1, Review of TCP/IP Protocol Suite and Python Language, reviews the fundamental technologies that make up Internet communication today, from the OSI and client-server models to TCP, UDP, and IP protocol suites. It will also review the basics of the Python language in its types, operators, loops, functions, and packages.

Chapter 2, Low-Level Network Device Interactions, uses practical examples to illustrate how to use Python to execute commands on a network device. It will discuss the challenges of having a CLI-only interface in automation. The chapter will use PExpect and Paramiko library examples.

Chapter 3, API and Intent-Driven Networking, discusses the newer network devices that support Application Program Interfaces (APIs) and other high-level interaction methods. It also illustrates a tool that allows network engineers to abstract the low-level tasks when scripting in Python while focusing on the design and what you want the network to achieve. A discussion of Cisco NX-API, Juniper PyEZ, and Arista PyEAPI among other technologies is also included.

Chapter 4, The Python Automation Framework - Ansible Basics, discusses the basics of Ansible, an open source, Python-based automation framework. Ansible goes one step further from APIs and focuses on network intents and device interaction. In this chapter, we will cover the advantages of using Ansible, its architecture, and practical examples of Ansible with Cisco, Juniper, and Arista devices.

Chapter 5, The Python Automation Framework - Ansible Advance Topics, builds on the knowledge obtained from the previous chapter and covers the more advanced Ansible concepts such as conditionals, loops, templates, variables, vaults, and roles. It will also introduce how to write your own Ansible module that fits in your network environment.

Chapter 6, Network Security with Python, introduces several Python tools to help you secure your network. It will discuss using Scapy for security testing, using Ansible to quickly implement access lists, and forensic analysis with syslog and UFW using Python.

Chapter 7, Network Monitoring with Python - Part 1, covers monitoring the network using various tools. It will use SNMP and PySNMP for queries to obtain device information. From the results, we will use Matplotlib and Pygal to visualize the results. The chapter will end with Cacti examples and how to use Python scripts as input source.

Chapter 8, Network Monitoring with Python - Part 2, covers more network-monitoring tools. It will start with using Graphviz to graph network graphs automatically from LLDP information. It will move to introducing push-based network monitoring using NetFlow and other similar technologies. We will use Python to decode flow packets as well as use ntop to visualize flow information. We will also introduce hosted Elasticsearch as a way to complement network monitoring.

Chapter 9, Building Network Web Services with Python, shows you how to use the Python web framework, Flask, to create your own API on the network level. The network-level API offers benefits such as abstracting the requester away from network details, consolidating and customizing operations, and better security by limiting the exposure of available operations.

Chapter 10, OpenFlow Basics, covers the basics of OpenFlow, a protocol that many credit as the technology that stared the software-defined networking movement. The protocol separates the control and data plane of network devices, which allows network operators to quickly prototype and innovate new features and functions. We will use the Python-based controller Ryu as well as Mininet to simulate an OpenFlow network. We will introduce examples of OpenFlow layer 2 switches and firewalls.

Chapter 11, AdvancedOpenFlow Topics, introduces advanced OpenFlow topics by building additional network applications and features using OpenFlow. We will start with building an OpenFlow router with static flows and then enhance the application with the REST API and build BGP speaking capabilities to interact with traditional networks. The chapter will end with using the firewall applications example as a way to virtualize traditional network functions.

Chapter 12, OpenStack, OpenDaylight, and NFV, covers other software-defined networking projects: OpenStack, OpenDaylight, and Network Function Virtualization. We will focus on the OpenStack network project, Neutron, in the chapter to discuss the service architecture and how to try out OpenStack with TryStack and DevStack. The chapter will also cover a basic OpenDaylight controller example for a simple hub with Mininet.

Chapter 13, Hybrid SDN, uses the knowledge from previous chapters and discusses various considerations and methods for implementing a software-driven network. We will discuss preparing your network for SDN and OpenFlow and considerations for greenfield deployment, controller redundancy, BGP interoperability, monitoring integration, controller secure TLS connection, and physical switch selection for your network.

It is strongly recommended that you follow and practice the examples given in this book. To complete the examples, you will need a host machine that runs Python 2.7 and 3.4, with enough administrative permissions to install the tools introduced in the book. The host machine can be a virtual machine and should preferably run a flavor of Linux. In the book, we'll use Ubuntu 16.04, but other Linux distributions should work as well. You might need to tweak your settings accordingly. In addition, either physical or virtual network equipment is needed to test your code.

This book is ideal for IT professionals and ops engineers who already manage groups of network devices and would like to expand their knowledge on using Python to overcome networking challenges. Basic knowledge of networking and Python are recommended.

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: We can include other contexts through the use of the include directive.

A block of code is set as follows:

 # This is a comment
    print("hello world") 

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

        [
          {
 "hosts": "192.168.199.170",
            "tasks": [
            "name": "check disk usage",
            "shell": "df > df_temp.txt"
           ]
          }
        ]

Any command-line input or output is written as follows:

$ ssh-keygen -t rsa <<<< generates public-private key pair on the host machine
$ cat ~/.ssh/id_rsa.pub <<<< copy the content of the output and paste it to the ~/.ssh/authorized_keys file on the target host

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: Clicking the Next button moves you to the next screen.

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