Gain insights into automating network reconnaissance, orchestrating repetitive changes, and transforming network configuration management. Discover CI/CD pipeline migration for full network automation.

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​​Network automation begins with automating network reconnaissance. This is accomplished by gathering important information from network devices while building a library of dynamic on-demand utilities and generating living documentation. Starting small, the course exhibits the simplicity and elegance of network automation.

Next, you will learn how to automate larger changes that require a high number of repetitive steps. These changes will be executed serially in a specific orchestrated order, making them perfect for an automated solution. After gaining comfort with the new tools, you can fully transform network configuration management to an automated, intent-based, self-documenting system.

The final step is learning how to migrate to a continuous integration/continuous delivery (CI/CD) pipeline, thereby fully automating the network.

Automate Your Network

# Basics
Even a beginner can write the basic logic statements required to create dynamic templates. Having
already created the data dictionary, it is now a simple matter of learning and understanding the syntax
required to unlock the information. The previous example, `01_ios_global.j2`, also contains some dynamic
templating required to handle the various unique platform differences or to substitute dynamic
information to variables. Here is the rest of the template that includes the logical statements. Note that there
are no spaces in the real template; they have been added to help with readability:

hostname {{ host_defaults.hostname }}
{%  if platform_defaults.type == 6000 %}
boot system bootdisk:{{ platform_defaults.boot }}
{%  endif %}
{%  if platform_defaults.type == 4000 %}
boot system bootflash:{{ host_defaults.boot }}
{%  endif %}
logging buffered 64000
{%  if host_defaults.logging_levels is defined %}
{%      for logging_level in host_defaults.logging_levels %}
{%          for logging_target in host_defaults.logging_levels[logging_level]  %}
logging {{ logging_target }} {{ logging_level }}
{%          endfor %}
{%      endfor %}
{%  endif %}
{%  if platform_defaults.type == 6000 or platform_defaults.type == 4000 %}
service compress-config
no ip bootp server
diagnostic bootup level complete
{%  endif %}
errdisable recovery interval 60
{%  if platform_defaults.type == 6000 or platform_defaults.type == 4000 or platform_defaults.type == 3850 %}
redundancy 
 mode sso
{%  endif %}
enable secret 5 {{ global_campus_defaults.enable_secret }}
username admin privilege 15 secret 5 {{ global_campus_defaults.enable_secret }}
aaa new-model
{%  if platform_defaults.type == 6000 %}
platform ip cef load-sharing ip-only
platform sub-interface maximum-vlan vlan-id 2048
platform sub-interface maximum-vlan enable
platform rate-limit layer2 port-security pkt 300 burst 10
no logging event link-status boot
logging event link-status default
{%  endif %}
{%  if platform_defaults.type == 3750 or platform_defaults.type == 3850  %}
stack-mac persistent timer 0
{%  endif %}
clock timezone est -5 0
clock summer-time EDT recurring
ip arp proxy disable
udld enable
no ip domain-lookup
ip domain-name {{ global_campus_defaults.domain }}
vtp domain NULL
vtp mode transparent
{%  if platform_defaults.type == 4000 %}
power redundancy-mode redundant
{%  endif %}
login on-failure log
login on-success log
spanning-tree mode rapid-pvst
spanning-tree extend system-id
{%  if host_spanning_tree_values is defined %}
{%      for host_spanning_tree_value in host_spanning_tree_values %}
{%          for vlan_list in host_spanning_tree_values[host_spanning_tree_value] %}
spanning-tree vlan {{ vlan_list }} priority {{ host_spanning_tree_value }}
{%          endfor %}
{%      endfor %}
{%  endif %}
{%  if platform_defaults.type == 3750 %}
port-channel load-balance src-dst-ip
{%  else %}
{%      if platform_defaults.type == 6000 %}
port-channel load-balance src-dst-mixed-ip-port
{%      else %}
{%         if platform_defaults.type == 4000 or platform_defaults.type == 3850 %}
port-channel load-balance src-dst-port
{%         endif %}
{%      endif %}
{%  endif %}
{%  if platform_defaults.type != 3850 %}
vlan internal allocation policy ascending
{%  endif %}
ip ssh version 2
{%  if platform_defaults.type == 3750 or platform_defaults.type == 2960 %}
{%  else %}
no ip forward-protocol nd
{%  endif %}
no ip http server
no ip http secure-server
logging trap debugging
{%  for logging_host in global_campus_defaults.logging_hosts %}
logging host {{ logging_host }}
{%  endfor %}

The template is composed of a mix of static explicit data replacement, `if`/`else`/`end if` logic, and `for` loop logic.

Every device requires a hostname. This is a good place to start looking closer at the format of the template.
```py
hostname {{ host_defaults.hostname }} 
```
The Cisco IOS command to configure a hostname is `hostname <desired hostname>`. This is present
on every IOS device, so should be set in a global or hostname template early in the configuration. This is because
it is near the top of the running-configuration. This variable is in the `host_vars` data dictionary. The
dictionary is called `host_defaults`, and the key-value pair is accessible as `.hostname`. 

A key-value pair is a
set of two linked data items: a **key**, which is a unique identifier for some item of data, and the **value**,
which is either the data that is identified or a pointer to the location of that data.

# If statement
Here is an explicitly evaluated `if` statement: 
```py
{%  if platform_defaults.type == 6000 %}
boot system bootdisk:{{ platform_defaults.boot }}
{%  endif %} 
```

If the value in the key-value pair _type_ in the data dictionary `platform_defaults` is equal to **6000**, add
the following configuration line to the template. Look up the value of the boot key-value pair in the data
dictionary `platform_defaults` and replace this variable with the information. 

A more complex example: 
```py
{%      if platform_defaults.type == 6000 %}
port-channel load-balance src-dst-mixed-ip-port
{%      else %}
{%         if platform_defaults.type == 4000 or platform_defaults.type == 3850 %}
port-channel load-balance src-dst-port
{%         endif %}
{%      endif %}
{%  endif %}
```

First, we will evaluate the value in the key-value pair _type_ in the data dictionary `platform_defaults`.

If the value equals **6000**, run the command `port-channel load-balance src-dst-mixed-ip-port`. Otherwise, if the same value equals **4000** or **3850**, run the command `port-channel load-balance src-dst-port`.

# For loop
Here is an example of a `for` loop: 
```py
{%  if host_spanning_tree_values is defined %}
{%      for host_spanning_tree_value in host_spanning_tree_values %}
{%          for vlan_list in host_spanning_tree_values[host_spanning_tree_value] %}
spanning-tree vlan {{ vlan_list }} priority {{ host_spanning_tree_value }}
{%          endfor %}
{%      endfor %}
{%  endif %}
```

This might look complicated, because there is a loop nested inside another loop. Scenarios exist where
it is required to nest loops. It is not that difficult if good syntax and a consistent approach is taken.

First, evaluate if the data dictionary `host_spanning_tree_values`, is defined. If so, loop through the list
`host_spanning_tree_values`. Each item in the list will also be a list: `vlan_list`. Notice the syntax used in
the second loop. Using square brackets and the name of the list item makes it human-readable.

Ultimately, it produces the line `spanning-tree vlan {{ vlan_list }} priority {{
host_spanning_tree_value }}` for each nested list item in the data dictionary. The following data model:

```text
host_spanning_tree_values:
  24576:
    - 2-3,10-13,20,30,50,100,200
```

This results in the following configuration: 
```text
spanning-tree vlan 2-3,10-13,20,30,50,100,200 priority 24576 
```

The template allows the configuration or intent to scale, as well as different priorities for different
lists of VLANs. 


Let's learn some basic programming concepts like "if" statements and "for" loops using the Jinja2 templates.

Introduction

What Is Network Automation?

Why Automate the Network?

How to Automate the Network

Where to Start with Network Automation

Repository Structure

Network Reconnaissance

Tactical Playbooks

Data Models and Dynamic Templates

Dynamic Intent-Based Documentation

Configuration Management

Continuous Integration/Continuous Delivery

Conclusion

Basic Programmatic Logic

Basics