{%- set ifaces = [] %}
{%- for iface, ips in salt['grains.get']('ip_interfaces').items() %}
{%-   if iface not in ['core', 'lo'] %}
{%-     set ifaces = ifaces.append(iface) %}
{%-   endif %}
{%- endfor %}

INTERFACESv4="{{ ' '.join(ifaces) }}"
INTERFACESv6=""