_network.html.erb

<div class="fields">
  <% if f.object._delete != '1' -%>
    <% disabled = (f.object.persisted? == "true" || f.object.persisted? == true) %>
    <%= text_f f, :name, :disabled => disabled, :class => "span2" %>
    <%= f.hidden_field :name if disabled %>
    <% selected_cluster = params[:host] && params[:host][:compute_attributes] && params[:host][:compute_attributes][:cluster] %>
    <% selected_cluster ||= clusters.size == 1 ? clusters.first.id : nil %>
    <%= select_f f, :network, compute_resource.networks(selected_cluster ? { :cluster_id => selected_cluster } : { }), :id, :name,
                 { }, :disabled => disabled, :class => "span2",
                 :help_inline   => remove_child_link("X", f, { :method => :'_delete', :title => 'remove network interface', :class => 'label important' }) %>
    <%= f.hidden_field :network if disabled %>
  <% end -%>
</div>