Error message is given if there are no auto ports available.

lib/vagrant/actions/vm/forward_ports.rb

@@ -46,6 +46,10 @@ module Vagrant
           range = runner.env.config.vm.auto_port_range.to_a
           range -= used_ports
 
+          if range.empty?
+            raise ActionException.new(:vm_port_auto_empty, :vm_name => @runner.name, :name => name, :options => options)
+          end
+
           # Set the port up to be the first one and add that port to
           # the used list.
           options[:hostport] = range.shift

templates/strings.yml

@@ -197,6 +197,13 @@
   The vagrant virtual environment you are trying to suspend must be running to be suspended.
 :vm_not_suspended: |-
   The vagrant virtual environment you are trying to resume is not in a suspended state.
+:vm_port_auto_empty: |-
+  Vagrant found a port collision for the specified port and virtual machine.
+  While this port was marked to be auto-corrected, the ports in the
+  auto-correction range are all also used.
+
+  VM: <%= vm_name %>
+  Forwarded port: <%= name %> (<%= options[:guestport] %> => <%= options[:hostport] %>)
 :vm_port_collision: |-
   Vagrant cannot forward the specified ports on this VM, since they
   would collide with another VirtualBox virtual machine's forwarded

test/test_helper.rb

@@ -101,6 +101,7 @@ class Test::Unit::TestCase
     action = action_klass.new(mock_vm, *args)
     stub_default_action_dependecies(action)
 
+    mock_vm.stubs(:name).returns("foo")
     mock_vm.stubs(:vm).returns(vm)
     mock_vm.stubs(:vm=)
     mock_vm.stubs(:invoke_callback)

test/vagrant/actions/vm/forward_ports_test.rb

@@ -72,7 +72,6 @@ class ForwardPortsActionTest < Test::Unit::TestCase
       @used_ports = [1,2,3]
 
       @runner.env.config.vm.auto_port_range = (1..5)
-      @auto_port_range = @runner.env.config.vm.auto_port_range.to_a
     end
 
     should "raise an exception if auto forwarding is disabled" do
@@ -94,6 +93,13 @@ class ForwardPortsActionTest < Test::Unit::TestCase
       @action.handle_collision(@name, @options, @used_ports)
       assert @used_ports.include?(4)
     end
+
+    should "raise an exception if there are no auto ports available" do
+      @runner.env.config.vm.auto_port_range = (1..3)
+      assert_raises(Vagrant::Actions::ActionException) {
+        @action.handle_collision(@name, @options, @used_ports)
+      }
+    end
   end
 
   context "execution" do