sonic-buildimage/files/build_templates/arp_update_vars.j2

{
    "interface": "{% for (name, prefix) in INTERFACE|pfx_filter %}{% if prefix|ipv6 %}{{ name }} {% endif %}{% endfor %}",
    "pc_interface" : "{% for (name, prefix) in PORTCHANNEL_INTERFACE|pfx_filter %}{% if prefix|ipv6 %}{{ name }} {% endif %}{% endfor %}",
    "vlan_sub_interface": "{% for (name, prefix) in VLAN_SUB_INTERFACE|pfx_filter %}{% if prefix|ipv6 %}{{ name }} {% endif %}{% endfor %}",
    "vlan" : "{% if VLAN %}{{ VLAN.keys() | join(' ') }}{% endif %}"
}