ceph-ansible/roles/ceph-common/templates/mon_addr_interface.j2

mon host = {% for host in groups[mon_group_name] %}{{ hostvars[host]['ansible_' + (hostvars[host]['monitor_interface'] if hostvars[host]['monitor_interface'] is defined else monitor_interface) ]['ipv4']['address'] }}{% if not loop.last %},{% endif %}{% endfor %}