neutron subnet-update xxx --dns_nameservers 1.1.1.1 2.2.2.2 3.3.3.3 the order will be: 1.1.1.1 2.2.2.2 3.3.3.3
neutron subnet-update xxx --dns_nameservers 1.1.1.1 2.2.2.2 3.3.3.3
the order will be: 1.1.1.1 2.2.2.2 3.3.3.3