diff --git a/lib/vagrant/action/builtin.rb b/lib/vagrant/action/builtin.rb
index 02c7d2095..f3536edcf 100644
--- a/lib/vagrant/action/builtin.rb
+++ b/lib/vagrant/action/builtin.rb
@@ -13,6 +13,7 @@ module Vagrant
         use VM::Customize
         use VM::ForwardPorts
         use VM::ShareFolders
+        use VM::Network
         use VM::Boot
       end
 
diff --git a/lib/vagrant/action/vm/network.rb b/lib/vagrant/action/vm/network.rb
new file mode 100644
index 000000000..3c3c184e9
--- /dev/null
+++ b/lib/vagrant/action/vm/network.rb
@@ -0,0 +1,137 @@
+module Vagrant
+  class Action
+    module VM
+      # Networking middleware for Vagrant. This enables host only
+      # networking on VMs if configured as such.
+      class Network
+        def initialize(app, env)
+          @app = app
+          @env = env
+
+          env["config"].vm.network_options.compact.each do |network_options|
+            if !verify_no_bridge_collision(network_options)
+              env.error!(:network_collides)
+              return
+            end
+          end
+        end
+
+        def call(env)
+          @env = env
+          assign_network if enable_network?
+
+          @app.call(env)
+
+          if !env.error? && enable_network?
+            @env.logger.info "Enabling host only network..."
+            @env["vm"].system.prepare_host_only_network
+            @env.env.config.vm.network_options.compact.each do |network_options|
+              @env["vm"].system.enable_host_only_network(network_options)
+            end
+          end
+        end
+
+        # Verifies that there is no collision with a bridged network interface
+        # for the given network options.
+        def verify_no_bridge_collision(net_options)
+          interfaces = VirtualBox::Global.global.host.network_interfaces
+          interfaces.each do |ni|
+            next if ni.interface_type == :host_only
+
+            result = if net_options[:name]
+              true if net_options[:name] == ni.name
+            else
+              true if matching_network?(ni, net_options)
+            end
+
+            return false if result
+          end
+
+          true
+        end
+
+        def enable_network?
+          !@env.env.config.vm.network_options.compact.empty?
+        end
+
+        # Enables and assigns the host only network to the proper
+        # adapter on the VM, and saves the adapter.
+        def assign_network
+          @env.logger.info "Preparing host only network..."
+
+          @env.env.config.vm.network_options.compact.each do |network_options|
+            adapter = @env["vm"].vm.network_adapters[network_options[:adapter]]
+            adapter.enabled = true
+            adapter.attachment_type = :host_only
+            adapter.host_interface = network_name(network_options)
+            adapter.save
+          end
+        end
+
+        # Returns the name of the proper host only network, or creates
+        # it if it does not exist. Vagrant determines if the host only
+        # network exists by comparing the netmask and the IP.
+        def network_name(net_options)
+          # First try to find a matching network
+          interfaces = VirtualBox::Global.global.host.network_interfaces
+          interfaces.each do |ni|
+            # Ignore non-host only interfaces which may also match,
+            # since they're not valid options.
+            next if ni.interface_type != :host_only
+
+            if net_options[:name]
+              return ni.name if net_options[:name] == ni.name
+            else
+              return ni.name if matching_network?(ni, net_options)
+            end
+          end
+
+          return @env.error!(:network_not_found, :name => net_options[:name]) if net_options[:name]
+
+          # One doesn't exist, create it.
+          @env.logger.info "Creating new host only network for environment..."
+
+          ni = interfaces.create
+          ni.enable_static(network_ip(net_options[:ip], net_options[:netmask]),
+                           net_options[:netmask])
+          ni.name
+        end
+
+        # Tests if a network matches the given options by applying the
+        # netmask to the IP of the network and also to the IP of the
+        # virtual machine and see if they match.
+        def matching_network?(interface, net_options)
+          interface.network_mask == net_options[:netmask] &&
+            apply_netmask(interface.ip_address, interface.network_mask) ==
+            apply_netmask(net_options[:ip], net_options[:netmask])
+        end
+
+        # Applies a netmask to an IP and returns the corresponding
+        # parts.
+        def apply_netmask(ip, netmask)
+          ip = split_ip(ip)
+          netmask = split_ip(netmask)
+
+          ip.map do |part|
+            part & netmask.shift
+          end
+        end
+
+        # Splits an IP and converts each portion into an int.
+        def split_ip(ip)
+          ip.split(".").map do |i|
+            i.to_i
+          end
+        end
+
+        # Returns a "network IP" which is a "good choice" for the IP
+        # for the actual network based on the netmask.
+        def network_ip(ip, netmask)
+          parts = apply_netmask(ip, netmask)
+          parts[3] += 1;
+          parts.join(".")
+        end
+      end
+    end
+  end
+end
diff --git a/test/vagrant/action/vm/network_test.rb b/test/vagrant/action/vm/network_test.rb
new file mode 100644
index 000000000..9769e078c
--- /dev/null
+++ b/test/vagrant/action/vm/network_test.rb
@@ -0,0 +1,246 @@
+require File.join(File.dirname(__FILE__), '..', '..', '..', 'test_helper')
+
+class NetworkVMActionTest < Test::Unit::TestCase
+  setup do
+    @klass = Vagrant::Action::VM::Network
+    @app, @env = mock_action_data
+
+    @vm = mock("vm")
+    @vm.stubs(:name).returns("foo")
+    @vm.stubs(:ssh).returns(mock("ssh"))
+    @vm.stubs(:system).returns(mock("system"))
+    @env["vm"] = @vm
+
+    @internal_vm = mock("internal")
+    @vm.stubs(:vm).returns(@internal_vm)
+  end
+
+  context "initializing" do
+    should "verify no bridge collisions for each network enabled" do
+      @env.env.config.vm.network("foo")
+      @klass.any_instance.expects(:verify_no_bridge_collision).once.with() do |options|
+        assert_equal "foo", options[:ip]
+        true
+      end
+
+      @klass.new(@app, @env)
+    end
+  end
+
+  context "with an instance" do
+    setup do
+      @klass.any_instance.stubs(:verify_no_bridge_collision)
+      @instance = @klass.new(@app, @env)
+
+      @interfaces = []
+      VirtualBox::Global.global.host.stubs(:network_interfaces).returns(@interfaces)
+    end
+
+    def mock_interface(options=nil)
+      options = {
+        :interface_type => :host_only,
+        :name => "foo"
+      }.merge(options || {})
+
+      interface = mock("interface")
+      options.each do |k,v|
+        interface.stubs(k).returns(v)
+      end
+
+      @interfaces << interface
+      interface
+    end
+
+    context "calling" do
+      setup do
+        @env.env.config.vm.network("foo")
+        @instance.stubs(:enable_network?).returns(false)
+      end
+
+      should "do nothing if network should not be enabled" do
+        @instance.expects(:assign_network).never
+        @app.expects(:call).with(@env).once
+        @vm.system.expects(:prepare_host_only_network).never
+        @vm.system.expects(:enable_host_only_network).never
+
+        @instance.call(@env)
+      end
+
+      should "assign and enable the network if networking enabled" do
+        @instance.stubs(:enable_network?).returns(true)
+
+        run_seq = sequence("run")
+        @instance.expects(:assign_network).once.in_sequence(run_seq)
+        @app.expects(:call).with(@env).once.in_sequence(run_seq)
+        @vm.system.expects(:prepare_host_only_network).once.in_sequence(run_seq)
+        @vm.system.expects(:enable_host_only_network).once.in_sequence(run_seq)
+
+        @instance.call(@env)
+      end
+    end
+
+    context "checking if network is enabled" do
+      should "return true if the network options are set" do
+        @env.env.config.vm.network("foo")
+        assert @instance.enable_network?
+      end
+
+      should "return false if the network was not set" do
+        assert !@instance.enable_network?
+      end
+    end
+
+    context "assigning the network" do
+      setup do
+        @network_name = "foo"
+        @instance.stubs(:network_name).returns(@network_name)
+
+        @network_adapters = []
+        @internal_vm.stubs(:network_adapters).returns(@network_adapters)
+
+        @options = {
+          :ip => "foo",
+          :adapter => 7
+        }
+
+        @env.env.config.vm.network(@options[:ip], @options)
+      end
+
+      should "setup the specified network adapter" do
+        adapter = mock("adapter")
+        @network_adapters[@options[:adapter]] = adapter
+
+        adapter.expects(:enabled=).with(true).once
+        adapter.expects(:attachment_type=).with(:host_only).once
+        adapter.expects(:host_interface=).with(@network_name).once
+        adapter.expects(:save).once
+
+        @instance.assign_network
+      end
+    end
+
+    context "network name" do
+      setup do
+        @instance.stubs(:matching_network?).returns(false)
+
+        @options = { :ip => :foo, :netmask => :bar, :name => nil }
+      end
+
+      should "return the network which matches" do
+        result = mock("result")
+        interface = mock_interface(:name => result)
+
+        @instance.expects(:matching_network?).with(interface, @options).returns(true)
+        assert_equal result, @instance.network_name(@options)
+      end
+
+      should "ignore non-host only interfaces" do
+        @options[:name] = "foo"
+        mock_interface(:name => @options[:name],
+                       :interface_type => :bridged)
+
+        @instance.network_name(@options)
+        assert @env.error?
+      end
+
+      should "return the network which matches the name if given" do
+        @options[:name] = "foo"
+
+        interface = mock_interface(:name => @options[:name])
+        assert_equal @options[:name], @instance.network_name(@options)
+      end
+
+      should "error and exit if the given network name is not found" do
+        @options[:name] = "foo"
+
+        @interfaces.expects(:create).never
+        @instance.network_name(@options)
+        assert @env.error?
+        assert_equal :network_not_found, @env.error.first
+      end
+
+      should "create a network for the IP and netmask" do
+        result = mock("result")
+        network_ip = :foo
+
+        interface = mock_interface(:name => result)
+        interface.expects(:enable_static).with(network_ip, @options[:netmask])
+        @interfaces.expects(:create).returns(interface)
+        @instance.expects(:network_ip).with(@options[:ip], @options[:netmask]).once.returns(network_ip)
+
+        assert_equal result, @instance.network_name(@options)
+      end
+    end
+
+    context "checking for a matching network" do
+      setup do
+        @interface = mock("interface")
+        @interface.stubs(:network_mask).returns("foo")
+        @interface.stubs(:ip_address).returns("192.168.0.1")
+
+        @options = {
+          :netmask => "foo",
+          :ip => "baz"
+        }
+      end
+
+      should "return false if the netmasks don't match" do
+        @options[:netmask] = "bar"
+        assert @interface.network_mask != @options[:netmask] # sanity
+        assert !@instance.matching_network?(@interface, @options)
+      end
+
+      should "return true if the netmasks yield the same IP" do
+        tests = [["255.255.255.0", "192.168.0.1", "192.168.0.45"],
+                 ["255.255.0.0", "192.168.45.1", "192.168.28.7"]]
+
+        tests.each do |netmask, interface_ip, guest_ip|
+          @options[:netmask] = netmask
+          @options[:ip] = guest_ip
+          @interface.stubs(:network_mask).returns(netmask)
+          @interface.stubs(:ip_address).returns(interface_ip)
+
+          assert @instance.matching_network?(@interface, @options)
+        end
+      end
+    end
+
+    context "applying the netmask" do
+      should "return the proper result" do
+        tests = {
+          ["192.168.0.1","255.255.255.0"] => [192,168,0,0],
+          ["192.168.45.10","255.255.255.0"] => [192,168,45,0]
+        }
+
+        tests.each do |k,v|
+          assert_equal v, @instance.apply_netmask(*k)
+        end
+      end
+    end
+
+    context "splitting an IP" do
+      should "return the proper result" do
+        tests = {
+          "192.168.0.1" => [192,168,0,1]
+        }
+
+        tests.each do |k,v|
+          assert_equal v, @instance.split_ip(k)
+        end
+      end
+    end
+
+    context "network IP" do
+      should "return the proper result" do
+        tests = {
+          ["192.168.0.45", "255.255.255.0"] => "192.168.0.1"
+        }
+
+        tests.each do |args, result|
+          assert_equal result, @instance.network_ip(*args)
+        end
+      end
+    end
+
+  end
+end