How to do it...

1. Install python3-pip and Python's netaddr library, since we will be using the Ansible IP filter, which requires Python's netaddr library:

# On ubuntu
$ sudo apt-get install python3-pip

# On CentOS
$ sudo yum install python3-pip

$ pip3 install netaddr

2. Create a new Ansible playbook called ansible_filters.yml, as shown here:

---
  - name: Ansible Filters
    hosts: csr1
    vars:
      interfaces:
        - { port: FastEthernet0/0, prefix: 10.1.1.0/24 }
        - { port: FastEthernet1/0, prefix: 10.1.2.0/24 }
    tasks:
      - name: Generate Interface Config
        blockinfile:
          block: |
            hostname {{ hostname | upper }}
            {% for intf in interfaces %}
            !
            interface {{ intf.port }}
              ip address {{intf.prefix | ipv4(1) | ipv4('address') }} {{intf.prefix | ipv4('netmask') }}
            !
            {% endfor %}
          dest: "configs/csr1_interfaces.cfg"
          create: yes
        delegate_to: localhost