def get_vlan_untag_ports(config_facts):
    """
    get all untag vlan ports
    """
    vlan_untag_ports = []
    vlans = config_facts.get('VLAN_INTERFACE', {}).keys()
    for vlan in vlans:
        vlan_member_info = config_facts.get('VLAN_MEMBER', {}).get(vlan, {})
        if vlan_member_info:
            for port_name, tag_mode in vlan_member_info.items():
                if tag_mode['tagging_mode'] == 'untagged':
                    vlan_untag_ports.append(port_name)

    return vlan_untag_ports