core-admin/templates/libvirt/devices/net.xml

<interface type="ethernet">
    <mac address="{{ vm.mac }}" />
    <ip address="{{ vm.ip }}" />
{% if vm.ip6 %}
    <ip address="{{ vm.ip6 }}" family='ipv6' />
{% endif %}
    <backenddomain name="{{ vm.netvm.name }}" />
    <script path="vif-route-qubes" />
</interface>

{# vim : set ft=jinja ts=4 sts=4 sw=4 et : #}