How it works...

In the group_vars/lan.yml file, we define a vlans list data structure that holds the VLAN definition that we need to apply to all our core and access switches. This variable will be available for all the core and access switches, and Ansible will use this variable in order to provision the required VLANs on the remote devices.

We use another declarative module, ios_vlan, which takes the VLAN definition (its name and the VLAN ID) and configures these VLANs on the remote managed device. It pulls the existing configuration from the device and compares it with the list of devices that need to be present, while only pushing the delta.

We use the loop construct to go through all the items in the vlans list, and configure all the respective VLANs on all the devices.

After running this task on the devices, the following is the output from one of the access switches:

access01#sh vlan
VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Et1/0, Et1/1, Et1/2, Et1/3
10   Data                             active    Et0/3
20   Voice                            active
100  Web                              active