config.j2

# Config file

{% for interface in interfaces %}
{% if interface.additional is defined and interface.additional %}
{% if interface.additional['border'] is defined and interface.additional['border'] %}
- id: 101
  kernel:
    name: {{ prefix_tables }}{{ interface.name }}
  ospf:
    scan_time: 20
    import: none
    export: all

{% endif %}
{% endif %}
{% endfor %}

result

# Config file

- id: 101
  kernel:
    name: prefix_eth0
  ospf:
    scan_time: 20
    import: none
    export: all

- id: 101
  kernel:
    name: prefix_eth1
  ospf:
    scan_time: 20
    import: none
    export: all