The code files for this chapter can be found here:

https://github.com/PacktPublishing/Network-Automation-Cookbook/tree/master/ch2_ios

The software releases that this chapter is based on are as follows:

• Cisco IOS 15.1
• Cisco IOS–XE 16.6.1
• Ansible 2.9
• Python 3.6.8

Check out the following video to see the Code in Action:
https://bit.ly/34F8xPW

In this recipe, we will outline how to build and structure the Ansible inventory to describe the network setup outlined in the previous section.

Make sure that Ansible is already installed on the control machine.

1. Create a new directory with the following name: ch2_ios.
2. Inside this new folder, create the hosts file with the following content:

$ cat hosts
 [access]
 access01 Ansible_host=172.20.1.18
 access02 Ansible_host=172.20.1.19

[core]
 core01 Ansible_host=172.20.1.20
 core02 Ansible_host=172.20.1...

In this recipe, we will outline how to connect to Cisco IOS devices from Ansible via SSH in order to start managing devices from Ansible.

In order to follow along with this recipe, an Ansible inventory file should be constructed as per the previous recipe. IP reachability between the Ansible control machine and all the devices in the network must be configured.

1. Inside the ch2_ios directory, create the groups_vars folder.
2. Inside the group_vars folder, create the network.yml file with the following...

In this recipe, we will outline how we can configure basic system parameters on Cisco IOS devices, such as setting the hostname, DNS server, and NTP servers. Following the network setup that we outlined at the start of this chapter, we will configure the following information on all the Cisco IOS devices:

• DNS servers 172.20.1.250 and 172.20.1.251
• NTP server 172.20.1.17

An Ansible inventory file must be present, as well as the configuration for Ansible to connect to the Cisco IOS devices via SSH.

1. To the...

In this recipe, we will outline how to configure the basic interface properties on Cisco IOS-based devices, such as setting the interface description, the interface maximum transmission unit (MTU), and enabling interfaces. We will configure all the links within our topology as having a link MTU of 1,500 and to be fully duplex.

To follow along with this recipe, an Ansible inventory is assumed to be already set up, as is IP reachability between the Ansible control node with the Cisco devices in place.

1. In...

In this recipe, we will outline how to configure L2 VLANs on Cisco IOS devices, as per the network topology discussed in the introduction to this chapter. We will outline how to declare VLANs as Ansible variables, and how to use suitable Ansible modules to provision these VLANs on the network.

We will be building on the previous recipes discussed in this chapter to continue to configure the L2 VLANs on all the LAN devices within our sample topology.

1. Update the group_vars/lan.yml file with the VLAN definition...

In this recipe, we will show how to configure access and trunk interfaces on Cisco IOS-based devices, and how to map interfaces to an access VLAN, as well as how to allow specific VLANs on the trunks.

Following our sample topology, we will configure the interfaces on the devices. As shown in this table, we are only showing the VLANs for access01 and core01— the other devices are exact replicas:

In this recipe, we will explore how to configure the interface IP address on Cisco IOS devices. We will use the sample topology to configure the VLAN interfaces on both the core switches. We will outline how to configure VRRP between the core switches for all the VLAN interfaces. We will configure the following IP addresses:

This recipe assumes that the interface and VLANs are configured as per the previous recipes in this chapter.

In this recipe, we will outline how to configure OSPF on Cisco IOS devices with Ansible. Using our sample network topology, we will set up OSPF between core switches and WAN routers, as well as advertising the SVI interface via OSPF.

This recipe assumes that all the interfaces are already configured with the correct IP addresses and are following the same procedures outlined in previous recipes.

1. Update the group_vars/core.yml file with the following data to define core links between core switches and WAN routers...

In this recipe, we will outline how to collect device facts from Cisco devices with Ansible. This information includes the serial number, IOS version, and all the interfaces on the devices. Ansible executes several commands on managed IOS devices in order to collect this information.

The Ansible controller must have IP connectivity with the managed network devices, and SSH must be enabled on the IOS devices.

1. Create a new playbook called pb_collect_facts.yml in the same ch2_ios folder with the following information...

In this recipe, we will outline how to validate network reachability via ping using Ansible. ICMP allows us to validate proper forwarding across our network. Using Ansible to perform this task provides us with a robust tool to validate proper traffic forwarding, since we can perform this task from each node simultaneously and collect all the results for further inspection.

This recipe is built based on the network setup that was outlined in the chapter introduction, and I am assuming that the network has already been built in accordance with all the previous recipes in this chapter.

In this recipe, we will outline how to execute operational commands on IOS devices and store these outputs to text files for further processing. This allows us to capture any operational commands from IOS devices during pre- or post-validation after we perform any deployment so that we can compare the results.

In order to follow along with this recipe, an Ansible inventory file should be in place and the network should already be set up as per the previous recipes.

1. Create a new playbook called...

In this recipe, we will outline how to use Ansible and the Cisco pyATS Python library to execute and parse operational commands on Cisco devices. Using these parsed commands, we can validate various aspects of the network.

This recipe assumes that the network has already been built and configured as outlined in all the previous recipes.

1. Install the Python libraries needed for pyATS:

$ sudo pip3 install pyats genie

2. Create the roles directory and then create the requirements.yml file with...