diff --git a/gns3server/module_manager.py b/gns3server/module_manager.py
index 6c7b28a4..876b09a9 100644
--- a/gns3server/module_manager.py
+++ b/gns3server/module_manager.py
@@ -82,8 +82,8 @@ class ModuleManager(object):
                                 log.info("loading {} module".format(module_class[0].lower()))
                                 info = Module(name=module_class[0].lower(), cls=module_class[1])
                                 self._modules.append(info)
-                except:
-                    log.warning("error while analyzing {} package directory".format(name))
+                except Exception as e:
+                    log.critical("error while analyzing {} package directory".format(name), exc_info=1)
                 finally:
                     if file:
                         file.close()
diff --git a/gns3server/modules/base.py b/gns3server/modules/base.py
index 7b4f3976..3f4d04f8 100644
--- a/gns3server/modules/base.py
+++ b/gns3server/modules/base.py
@@ -93,9 +93,16 @@ class IModule(multiprocessing.Process):
             stream.on_recv(callback)
         return stream
 
-#     def add_periodic_callback(self, callback, time):
-# 
-#         self.test = zmq.eventloop.ioloop.PeriodicCallback(callback, time, self._ioloop).start()
+    def add_periodic_callback(self, callback, time):
+        """
+        Adds a periodic callback to the ioloop.
+
+        :param callback: callback to be called
+        :param time: frequency when the callback is executed
+        """
+
+        periodic_callback = zmq.eventloop.ioloop.PeriodicCallback(callback, time, self._ioloop)
+        return periodic_callback
 
     def run(self):
         """
diff --git a/gns3server/modules/dynamips/__init__.py b/gns3server/modules/dynamips/__init__.py
index e6c8e8e8..b5599d03 100644
--- a/gns3server/modules/dynamips/__init__.py
+++ b/gns3server/modules/dynamips/__init__.py
@@ -19,6 +19,8 @@
 Dynamips server module.
 """
 
+import os
+import tempfile
 from gns3server.modules import IModule
 import gns3server.jsonrpc as jsonrpc
 
@@ -99,12 +101,16 @@ class Dynamips(IModule):
         IModule.__init__(self, name=name, args=args, kwargs=kwargs)
 
         self._hypervisor_manager = None
+        self._remote_server = False
         self._routers = {}
         self._ethernet_switches = {}
         self._frame_relay_switches = {}
         self._atm_switches = {}
         self._ethernet_hubs = {}
 
+        #self._callback = self.add_periodic_callback(self.test, 1000)
+        #self._callback.start()
+
     def stop(self):
         """
         Properly stops the module.
@@ -148,6 +154,8 @@ class Dynamips(IModule):
         self._frame_relay_switches.clear()
         self._atm_switches.clear()
 
+        self._hypervisor_manager = None
+        self._remote_server = False
         log.info("dynamips module has been reset")
 
     @IModule.route("dynamips.settings")
@@ -155,6 +163,12 @@ class Dynamips(IModule):
         """
         Set or update settings.
 
+        Mandatory request parameters:
+        - path (path to the Dynamips executable)
+
+        Optional request parameters:
+        - working_dir (path to a working directory)
+
         :param request: JSON request
         """
 
@@ -167,9 +181,32 @@ class Dynamips(IModule):
         #TODO: JSON schema validation
         # starts the hypervisor manager if it hasn't been started yet
         if not self._hypervisor_manager:
-            #TODO: working dir support
-            log.info("starting the hypervisor manager with Dynamips working directory set to '{}'".format("/tmp"))
-            self._hypervisor_manager = HypervisorManager(request["path"], "/tmp")
+            dynamips_path = request["path"]
+
+            if "working_dir" in request:
+                working_dir = request["working_dir"]
+                log.info("this server is local")
+            else:
+                self._remote_server = True
+                log.info("this server is remote")
+                try:
+                    working_dir = tempfile.mkdtemp(prefix="gns3-remote-server-")
+                    working_dir = os.path.join(working_dir, "dynamips")
+                    os.makedirs(working_dir)
+                    log.info("temporary working directory created: {}".format(working_dir))
+                except EnvironmentError as e:
+                    raise DynamipsError("Could not create temporary working directory: {}".format(e))
+
+            #TODO: check if executable
+            if not os.path.exists(dynamips_path):
+                raise DynamipsError("Dynamips executable {} doesn't exist".format(working_dir))
+
+            #TODO: check if writable
+            if not os.path.exists(working_dir):
+                raise DynamipsError("Working directory {} doesn't exist".format(working_dir))
+
+            log.info("starting the hypervisor manager with Dynamips working directory set to '{}'".format(working_dir))
+            self._hypervisor_manager = HypervisorManager(dynamips_path, working_dir)
 
         # apply settings to the hypervisor manager
         for name, value in request.items():
@@ -305,6 +342,28 @@ class Dynamips(IModule):
             router.ghost_status = 2
             router.ghost_file = ghost_instance
 
+#     def get_base64_config(self, config_path, router):
+#         """
+#         Get the base64 encoded config from a file.
+#         Replaces %h by the router name.
+# 
+#         :param config_path: path to the configuration file.
+#         :param router: Router instance.
+# 
+#         :returns: base64 encoded string
+#         """
+# 
+#         try:
+#             with open(config_path, "r") as f:
+#                 log.info("opening configuration file: {}".format(config_path))
+#                 config = f.read()
+#                 config = '!\n' + config.replace('\r', "")
+#                 config = config.replace('%h', router.name)
+#                 encoded = ("").join(base64.encodestring(config.encode("utf-8")).decode("utf-8").split())
+#                 return encoded
+#         except EnvironmentError as e:
+#             raise DynamipsError("Cannot parse {}: {}".format(config_path, e))
+
     @IModule.route("dynamips.nio.get_interfaces")
     def nio_get_interfaces(self, request):
         """
diff --git a/gns3server/modules/dynamips/backends/vm.py b/gns3server/modules/dynamips/backends/vm.py
index 14cfa9fb..8486ea34 100644
--- a/gns3server/modules/dynamips/backends/vm.py
+++ b/gns3server/modules/dynamips/backends/vm.py
@@ -16,6 +16,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import os
+import base64
 from gns3server.modules import IModule
 from ..dynamips_error import DynamipsError
 
@@ -121,8 +122,13 @@ class VM(object):
         platform = request["platform"]
         image = request["image"]
         ram = request["ram"]
+        hypervisor = None
 
         try:
+
+            if not self._hypervisor_manager:
+                raise DynamipsError("Dynamips manager is not started")
+
             hypervisor = self._hypervisor_manager.allocate_hypervisor_for_router(image, ram)
 
             router = PLATFORMS[platform](hypervisor, name)
@@ -158,11 +164,14 @@ class VM(object):
                 self.set_ghost_ios(router)
 
         except DynamipsError as e:
-            hypervisor.decrease_memory_load(ram)
-            if hypervisor.memory_load == 0 and not hypervisor.devices:
-                hypervisor.stop()
-                self._hypervisor_manager.hypervisors.remove(hypervisor)
-            self.send_custom_error(str(e))
+            dynamips_stdout = ""
+            if hypervisor:
+                hypervisor.decrease_memory_load(ram)
+                if hypervisor.memory_load == 0 and not hypervisor.devices:
+                    hypervisor.stop()
+                    self._hypervisor_manager.hypervisors.remove(hypervisor)
+                dynamips_stdout = hypervisor.read_stdout()
+            self.send_custom_error(str(e) + dynamips_stdout)
             return
 
         response = {"name": router.name,
@@ -330,6 +339,7 @@ class VM(object):
 
         Optional request parameters:
         - any setting to update
+        - startup_config_base64 (startup-config base64 encoded)
 
         Response parameters:
         - same as original request
@@ -346,6 +356,32 @@ class VM(object):
         router_id = request["id"]
         router = self._routers[router_id]
 
+        try:
+            # a new startup-config has been pushed
+            if "startup_config_base64" in request:
+                config = base64.decodestring(request["startup_config_base64"].encode("utf-8")).decode("utf-8")
+                config = "!\n" + config.replace("\r", "")
+                config = config.replace('%h', router.name)
+                config_dir = os.path.join(router.hypervisor.working_dir, "configs")
+                if not os.path.exists(config_dir):
+                    try:
+                        os.makedirs(config_dir)
+                    except EnvironmentError as e:
+                        raise DynamipsError("Could not create configs directory: {}".format(e))
+                config_path = os.path.join(config_dir, "{}.cfg".format(router.name))
+                try:
+                    with open(config_path, "w") as f:
+                        log.info("saving startup-config to {}".format(config_path))
+                        f.write(config)
+                except EnvironmentError as e:
+                    raise DynamipsError("Could not save the configuration {}: {}".format(config_path, e))
+                request["startup_config"] = "configs" + os.sep + os.path.basename(config_path)
+            if "startup_config" in request:
+                router.set_config(request["startup_config"])
+        except DynamipsError as e:
+            self.send_custom_error(str(e))
+            return
+
         # update the settings
         for name, value in request.items():
             if hasattr(router, name) and getattr(router, name) != value:
@@ -370,7 +406,7 @@ class VM(object):
                 if router.slots[slot_id]:
                     try:
                         router.slot_remove_binding(slot_id)
-                    except:
+                    except DynamipsError as e:
                         self.send_custom_error(str(e))
                         return
             elif name.startswith("wic") and value in WIC_MATRIX:
@@ -387,7 +423,11 @@ class VM(object):
             elif name.startswith("wic") and value == None:
                 wic_slot_id = int(name[-1])
                 if router.slots[0].wics and router.slots[0].wics[wic_slot_id]:
-                    router.uninstall_wic(wic_slot_id)
+                    try:
+                        router.uninstall_wic(wic_slot_id)
+                    except DynamipsError as e:
+                        self.send_custom_error(str(e))
+                        return
 
         # Update the ghost IOS file in case the RAM size has changed
         if self._hypervisor_manager.ghost_ios_support:
@@ -396,6 +436,40 @@ class VM(object):
         # for now send back the original request
         self.send_response(request)
 
+    @IModule.route("dynamips.vm.save_config")
+    def vm_save_config(self, request):
+        """
+        Save the configs for a VM (router).
+
+        Mandatory request parameters:
+        - id (vm identifier)
+        """
+
+        if request == None:
+            self.send_param_error()
+            return
+
+        #TODO: JSON schema validation for the request
+        log.debug("received request {}".format(request))
+        router_id = request["id"]
+        router = self._routers[router_id]
+        try:
+            if router.startup_config:
+                #TODO: handle private-config
+                startup_config_base64, _ = router.extract_config()
+                if startup_config_base64:
+                    try:
+                        config = base64.decodestring(startup_config_base64.encode("utf-8")).decode("utf-8")
+                        config = "!\n" + config.replace("\r", "")
+                        config_path = os.path.join(router.hypervisor.working_dir, router.startup_config)
+                        with open(config_path, "w") as f:
+                            log.info("saving startup-config to {}".format(router.startup_config))
+                            f.write(config)
+                    except EnvironmentError as e:
+                        raise DynamipsError("Could not save the configuration {}: {}".format(config_path, e))
+        except DynamipsError as e:
+            log.warn("could not save config to {}: {}".format(router.startup_config, e))
+
     @IModule.route("dynamips.vm.idlepcs")
     def vm_idlepcs(self, request):
         """
diff --git a/gns3server/modules/dynamips/dynamips_hypervisor.py b/gns3server/modules/dynamips/dynamips_hypervisor.py
index 8ad17a90..c4d554bd 100644
--- a/gns3server/modules/dynamips/dynamips_hypervisor.py
+++ b/gns3server/modules/dynamips/dynamips_hypervisor.py
@@ -33,6 +33,7 @@ class DynamipsHypervisor(object):
     """
     Creates a new connection to a Dynamips server (also called hypervisor)
 
+    :param working_dir: working directory
     :param host: the hostname or ip address string of the Dynamips server
     :param port: the tcp port integer (defaults to 7200)
     :param timeout: timeout integer for how long to wait for a response to commands sent to the
@@ -43,7 +44,7 @@ class DynamipsHypervisor(object):
     error_re = re.compile(r"""^2[0-9]{2}-""")
     success_re = re.compile(r"""^1[0-9]{2}\s{1}""")
 
-    def __init__(self, host, port=7200, timeout=30.0):
+    def __init__(self, working_dir, host, port=7200, timeout=30.0):
 
         self._host = host
         self._port = port
@@ -51,7 +52,7 @@ class DynamipsHypervisor(object):
         self._devices = []
         self._ghosts = {}
         self._jitsharing_groups = {}
-        self._working_dir = ""
+        self._working_dir = working_dir
         self._baseconsole = 2000
         self._baseaux = 2100
         self._baseudp = 10000
@@ -155,6 +156,7 @@ class DynamipsHypervisor(object):
         # encase working_dir in quotes to protect spaces in the path
         self.send("hypervisor working_dir {}".format('"' + working_dir + '"'))
         self._working_dir = working_dir
+        log.debug("working directory set to {}".format(self._working_dir))
 
     def save_config(self, filename):
         """
@@ -332,38 +334,58 @@ class DynamipsHypervisor(object):
 
         return self._port
 
-    def allocate_udp_port(self, max_port=100):
+    @staticmethod
+    def find_unused_port(start_port, end_port, host='127.0.0.1', socket_type="TCP"):
         """
-        Allocates a new UDP port for creating an UDP NIO.
-
-        :param max_port: maximum number of port to scan in
-        order to find one available for use.
+        Finds an unused port in a range.
 
-        :returns: port number (integer)
+        :param start_port: first port in the range
+        :param end_port: last port in the range
+        :param host: host/address for bind()
+        :param socket_type: TCP (default) or UDP
         """
 
-        #FIXME: better check for IPv6
-        start_port = self._current_udp_port
-        end_port = start_port + max_port
+        if socket_type == "UDP":
+            socket_type = socket.SOCK_DGRAM
+        else:
+            socket_type = socket.SOCK_STREAM
+
         for port in range(start_port, end_port):
             if port > end_port:
-                raise DynamipsError("Could not find a free port between {0} and {1}".format(start_port, max_port))
+                raise DynamipsError("Could not find a free port between {0} and {1}".format(start_port, end_port))
             try:
-                if self.host.__contains__(':'):
+                if ":" in host:
                     # IPv6 address support
-                    s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
+                    s = socket.socket(socket.AF_INET6, socket_type)
                 else:
-                    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+                    s = socket.socket(socket.AF_INET, socket_type)
                 # the port is available if bind is a success
-                s.bind((self._host, port))
-                #FIXME: increment?
-                self._current_udp_port += 1
+                s.bind((host, port))
                 return port
             except socket.error as e:
                 if e.errno == errno.EADDRINUSE:  # socket already in use
                     continue
                 else:
-                    raise DynamipsError("UDP port allocation: {}".format(e))
+                    raise DynamipsError("Could not find an unused port: {}".format(e))
+
+    def allocate_udp_port(self, max_port=100):
+        """
+        Allocates a new UDP port for creating an UDP NIO.
+
+        :param max_port: maximum number of port to scan in
+        order to find one available for use.
+
+        :returns: port number (integer)
+        """
+
+        start_port = self._current_udp_port
+        end_port = start_port + max_port
+        allocated_port = DynamipsHypervisor.find_unused_port(start_port, end_port, self._host, socket_type="UDP")
+        if allocated_port - self._current_udp_port > 1:
+            self._current_udp_port += allocated_port - self._current_udp_port
+        else:
+            self._current_udp_port += 1
+        return allocated_port
 
     def send_raw(self, string):
         """
diff --git a/gns3server/modules/dynamips/hypervisor.py b/gns3server/modules/dynamips/hypervisor.py
index 31e86909..98082aa6 100644
--- a/gns3server/modules/dynamips/hypervisor.py
+++ b/gns3server/modules/dynamips/hypervisor.py
@@ -22,11 +22,12 @@ Represents a Dynamips hypervisor and starts/stops the associated Dynamips proces
 import os
 import time
 import subprocess
-import logging
 
 from .dynamips_hypervisor import DynamipsHypervisor
+from .dynamips_error import DynamipsError
 
-logger = logging.getLogger(__name__)
+import logging
+log = logging.getLogger(__name__)
 
 
 class Hypervisor(DynamipsHypervisor):
@@ -34,26 +35,25 @@ class Hypervisor(DynamipsHypervisor):
     Hypervisor.
 
     :param path: path to Dynamips executable
-    :param workingdir: working directory
+    :param working_dir: working directory
     :param port: port for this hypervisor
     :param host: host/address for this hypervisor
     """
 
     _instance_count = 0
 
-    def __init__(self, path, workingdir, host, port):
+    def __init__(self, path, working_dir, host, port):
 
-        DynamipsHypervisor.__init__(self, host, port)
+        DynamipsHypervisor.__init__(self, working_dir, host, port)
 
         # create an unique ID
         self._id = Hypervisor._instance_count
         Hypervisor._instance_count += 1
 
         self._path = path
-        self._workingdir = workingdir
         self._command = []
         self._process = None
-        self._stdout = None
+        self._stdout_file = ""
 
         # settings used the load-balance hypervisors
         # (for the hypervisor manager)
@@ -130,26 +130,6 @@ class Hypervisor(DynamipsHypervisor):
 
         self._host = host
 
-    @property
-    def workingdir(self):
-        """
-        Returns the working directory used to start the Dynamips hypervisor.
-
-        :returns: path to a working directory
-        """
-
-        return(self._workingdir)
-
-    @workingdir.setter
-    def workingdir(self, workingdir):
-        """
-        Sets the working directory used to start the Dynamips hypervisor.
-
-        :param workingdir: path to a working directory
-        """
-
-        self._workingdir = workingdir
-
     @property
     def image_ref(self):
         """
@@ -210,20 +190,18 @@ class Hypervisor(DynamipsHypervisor):
 
         self._command = self._build_command()
         try:
-            logger.info("Starting Dynamips: {}".format(self._command))
-            # TODO: create unique filename for stdout
-            self.stdout_file = os.path.join(self._workingdir, "dynamips.log")
-            fd = open(self.stdout_file, "w")
-            # TODO: check for exceptions and if process has already been started
-            self._process = subprocess.Popen(self._command,
-                                             stdout=fd,
-                                             stderr=subprocess.STDOUT,
-                                             cwd=self._workingdir)
-            logger.info("Dynamips started PID={}".format(self._process.pid))
-        except OSError as e:
-            logger.error("Could not start Dynamips: {}".format(e))
-        finally:
-            fd.close()
+            log.info("starting Dynamips: {}".format(self._command))
+            self._stdout_file = os.path.join(self._working_dir, "dynamips-{}.log".format(self._port))
+            log.info("logging to {}".format(self._stdout_file))
+            with open(self._stdout_file, "w") as fd:
+                self._process = subprocess.Popen(self._command,
+                                                 stdout=fd,
+                                                 stderr=subprocess.STDOUT,
+                                                 cwd=self._working_dir)
+            log.info("Dynamips started PID={}".format(self._process.pid))
+        except EnvironmentError as e:
+            log.error("could not start Dynamips: {}".format(e))
+            raise DynamipsError("could not start Dynamips: {}".format(e))
 
     def stop(self):
         """
@@ -232,7 +210,7 @@ class Hypervisor(DynamipsHypervisor):
 
         if self.is_running():
             DynamipsHypervisor.stop(self)
-            logger.info("Stopping Dynamips PID={}".format(self._process.pid))
+            log.info("stopping Dynamips PID={}".format(self._process.pid))
             # give some time for the hypervisor to properly stop.
             # time to delete UNIX NIOs for instance.
             time.sleep(0.01)
@@ -245,9 +223,13 @@ class Hypervisor(DynamipsHypervisor):
         Only use when the process has been stopped or has crashed.
         """
 
-        # TODO: check for exceptions
-        with open(self.stdout_file) as file:
-            output = file.read()
+        output = ""
+        if self._stdout_file:
+            try:
+                with open(self._stdout_file) as file:
+                    output = file.read()
+            except EnvironmentError as e:
+                log.warn("could not read {}: {}".format(self._stdout_file, e))
         return output
 
     def is_running(self):
diff --git a/gns3server/modules/dynamips/hypervisor_manager.py b/gns3server/modules/dynamips/hypervisor_manager.py
index 7ed84f68..1a5a7c01 100644
--- a/gns3server/modules/dynamips/hypervisor_manager.py
+++ b/gns3server/modules/dynamips/hypervisor_manager.py
@@ -19,8 +19,8 @@
 Manages Dynamips hypervisors (load-balancing etc.)
 """
 
-from __future__ import unicode_literals
 from .hypervisor import Hypervisor
+from .dynamips_error import DynamipsError
 import socket
 import time
 import logging
@@ -33,7 +33,7 @@ class HypervisorManager(object):
     Manages Dynamips hypervisors.
 
     :param path: path to the Dynamips executable
-    :param workingdir: path to a working directory
+    :param working_dir: path to a working directory
     :param host: host/address for hypervisors to listen to
     :param base_port: base TCP port for hypervisors
     :param base_console: base TCP port for consoles
@@ -43,7 +43,7 @@ class HypervisorManager(object):
 
     def __init__(self,
                  path,
-                 workingdir,
+                 working_dir,
                  host='127.0.0.1',
                  base_hypervisor_port=7200,
                  base_console_port=2000,
@@ -52,7 +52,7 @@ class HypervisorManager(object):
 
         self._hypervisors = []
         self._path = path
-        self._workingdir = workingdir
+        self._working_dir = working_dir
         self._host = host
         self._base_hypervisor_port = base_hypervisor_port
         self._current_port = self._base_hypervisor_port
@@ -108,25 +108,29 @@ class HypervisorManager(object):
         log.info("Dynamips path set to {}".format(self._path))
 
     @property
-    def workingdir(self):
+    def working_dir(self):
         """
         Returns the Dynamips working directory path.
 
         :returns: path to Dynamips working directory
         """
 
-        return self._workingdir
+        return self._working_dir
 
-    @workingdir.setter
-    def workingdir(self, workingdir):
+    @working_dir.setter
+    def working_dir(self, working_dir):
         """
         Sets a new path to the Dynamips working directory.
 
-        :param workingdir: path to Dynamips working directory
+        :param working_dir: path to Dynamips working directory
         """
 
-        self._workingdir = workingdir
-        log.info("working directory set to {}".format(self._workingdir))
+        self._working_dir = working_dir
+        log.info("working directory set to {}".format(self._working_dir))
+
+        # update all existing hypervisors with the new working directory
+        for hypervisor in self._hypervisors:
+            hypervisor.working_dir = working_dir
 
     @property
     def base_hypervisor_port(self):
@@ -406,16 +410,12 @@ class HypervisorManager(object):
         # try to connect for 10 seconds
         while(time.time() - begin < 10.0):
             time.sleep(0.01)
-            sock = None
             try:
-                sock = socket.create_connection((host, port), timeout)
+                with socket.create_connection((host, port), timeout):
+                    pass
             except socket.error as e:
                 last_exception = e
-                #time.sleep(0.01)
                 continue
-            finally:
-                if sock:
-                    sock.close()
             connection_success = True
             break
 
@@ -426,6 +426,25 @@ class HypervisorManager(object):
         else:
             log.info("Dynamips server ready after {:.4f} seconds".format(time.time() - begin))
 
+    def allocate_tcp_port(self, max_port=100):
+        """
+        Allocates a new TCP port for a Dynamips hypervisor.
+
+        :param max_port: maximum number of port to scan in
+        order to find one available for use.
+
+        :returns: port number (integer)
+        """
+
+        start_port = self._current_port
+        end_port = start_port + max_port
+        allocated_port = Hypervisor.find_unused_port(start_port, end_port, self._host)
+        if allocated_port - self._current_port > 1:
+            self._current_port += allocated_port - self._current_port
+        else:
+            self._current_port += 1
+        return allocated_port
+
     def start_new_hypervisor(self):
         """
         Creates a new Dynamips process and start it.
@@ -433,15 +452,23 @@ class HypervisorManager(object):
         :returns: the new hypervisor instance
         """
 
+        port = self.allocate_tcp_port()
+#         working_dir = os.path.join(self._working_dir, "instance-{}".format(port))
+#         if not os.path.exists(working_dir):
+#             try:
+#                 os.makedirs(working_dir)
+#             except EnvironmentError as e:
+#                 raise DynamipsError("{}".format(e))
+
         hypervisor = Hypervisor(self._path,
-                                self._workingdir,
+                                self._working_dir,
                                 self._host,
-                                self._current_port)
+                                port)
 
         log.info("creating new hypervisor {}:{}".format(hypervisor.host, hypervisor.port))
         hypervisor.start()
 
-        self.wait_for_hypervisor(self._host, self._current_port)
+        self.wait_for_hypervisor(self._host, port)
         log.info("hypervisor {}:{} has successfully started".format(hypervisor.host, hypervisor.port))
 
         hypervisor.connect()
@@ -450,7 +477,6 @@ class HypervisorManager(object):
         hypervisor.baseudp = self._current_base_udp_port
         self._current_base_udp_port += self._udp_incrementation_per_hypervisor
         self._hypervisors.append(hypervisor)
-        self._current_port += 1
         return hypervisor
 
     def allocate_hypervisor_for_router(self, router_ios_image, router_ram):
diff --git a/gns3server/modules/dynamips/nodes/atm_bridge.py b/gns3server/modules/dynamips/nodes/atm_bridge.py
index c98975f8..036cfb5d 100644
--- a/gns3server/modules/dynamips/nodes/atm_bridge.py
+++ b/gns3server/modules/dynamips/nodes/atm_bridge.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual ATM bridge module ("atm_bridge").
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L622
 """
 
-from __future__ import unicode_literals
 from ..dynamips_error import DynamipsError
 
 
diff --git a/gns3server/modules/dynamips/nodes/atm_switch.py b/gns3server/modules/dynamips/nodes/atm_switch.py
index d4431a46..eecd9544 100644
--- a/gns3server/modules/dynamips/nodes/atm_switch.py
+++ b/gns3server/modules/dynamips/nodes/atm_switch.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual ATM switch module ("atmsw").
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L593
 """
 
-from __future__ import unicode_literals
 from ..dynamips_error import DynamipsError
 
 import logging
diff --git a/gns3server/modules/dynamips/nodes/bridge.py b/gns3server/modules/dynamips/nodes/bridge.py
index 1a4ae08d..a47bf654 100644
--- a/gns3server/modules/dynamips/nodes/bridge.py
+++ b/gns3server/modules/dynamips/nodes/bridge.py
@@ -20,8 +20,6 @@ Interface for Dynamips NIO bridge module ("nio_bridge").
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L538
 """
 
-from __future__ import unicode_literals
-
 
 class Bridge(object):
     """
@@ -36,6 +34,7 @@ class Bridge(object):
     def __init__(self, hypervisor, name):
 
         self._hypervisor = hypervisor
+        self._allocated_names.append(name)
         self._name = '"' + name + '"'  # put name into quotes to protect spaces
         self._hypervisor.send("nio_bridge create {}".format(self._name))
         self._hypervisor.devices.append(self)
diff --git a/gns3server/modules/dynamips/nodes/c1700.py b/gns3server/modules/dynamips/nodes/c1700.py
index 0943a9c2..51318790 100644
--- a/gns3server/modules/dynamips/nodes/c1700.py
+++ b/gns3server/modules/dynamips/nodes/c1700.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual Cisco 1700 instances module ("c1700")
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L428
 """
 
-from __future__ import unicode_literals
 from .router import Router
 from ..adapters.c1700_mb_1fe import C1700_MB_1FE
 from ..adapters.c1700_mb_wic1 import C1700_MB_WIC1
diff --git a/gns3server/modules/dynamips/nodes/c2600.py b/gns3server/modules/dynamips/nodes/c2600.py
index bc961d2c..e7f5b61a 100644
--- a/gns3server/modules/dynamips/nodes/c2600.py
+++ b/gns3server/modules/dynamips/nodes/c2600.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual Cisco 2600 instances module ("c2600")
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L404
 """
 
-from __future__ import unicode_literals
 from .router import Router
 from ..adapters.c2600_mb_1e import C2600_MB_1E
 from ..adapters.c2600_mb_2e import C2600_MB_2E
diff --git a/gns3server/modules/dynamips/nodes/c2691.py b/gns3server/modules/dynamips/nodes/c2691.py
index f846f1ac..9ba7e396 100644
--- a/gns3server/modules/dynamips/nodes/c2691.py
+++ b/gns3server/modules/dynamips/nodes/c2691.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual Cisco 2691 instances module ("c2691")
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L387
 """
 
-from __future__ import unicode_literals
 from .router import Router
 from ..adapters.gt96100_fe import GT96100_FE
 
diff --git a/gns3server/modules/dynamips/nodes/c3600.py b/gns3server/modules/dynamips/nodes/c3600.py
index 62230829..ccbd565c 100644
--- a/gns3server/modules/dynamips/nodes/c3600.py
+++ b/gns3server/modules/dynamips/nodes/c3600.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual Cisco 3600 instances module ("c3600")
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L366
 """
 
-from __future__ import unicode_literals
 from .router import Router
 from ..adapters.leopard_2fe import Leopard_2FE
 
diff --git a/gns3server/modules/dynamips/nodes/c3725.py b/gns3server/modules/dynamips/nodes/c3725.py
index d1bb39dc..d32fab1b 100644
--- a/gns3server/modules/dynamips/nodes/c3725.py
+++ b/gns3server/modules/dynamips/nodes/c3725.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual Cisco 3725 instances module ("c3725")
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L346
 """
 
-from __future__ import unicode_literals
 from .router import Router
 from ..adapters.gt96100_fe import GT96100_FE
 
diff --git a/gns3server/modules/dynamips/nodes/c3745.py b/gns3server/modules/dynamips/nodes/c3745.py
index db6d69bb..5c0ea13c 100644
--- a/gns3server/modules/dynamips/nodes/c3745.py
+++ b/gns3server/modules/dynamips/nodes/c3745.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual Cisco 3745 instances module ("c3745")
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L326
 """
 
-from __future__ import unicode_literals
 from .router import Router
 from ..adapters.gt96100_fe import GT96100_FE
 
diff --git a/gns3server/modules/dynamips/nodes/c7200.py b/gns3server/modules/dynamips/nodes/c7200.py
index 7164e3b5..0d73d3fc 100644
--- a/gns3server/modules/dynamips/nodes/c7200.py
+++ b/gns3server/modules/dynamips/nodes/c7200.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual Cisco 7200 instances module ("c7200")
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L294
 """
 
-from __future__ import unicode_literals
 from ..dynamips_error import DynamipsError
 from .router import Router
 from ..adapters.c7200_io_2fe import C7200_IO_2FE
diff --git a/gns3server/modules/dynamips/nodes/ethernet_switch.py b/gns3server/modules/dynamips/nodes/ethernet_switch.py
index 3b7379bf..83ddf080 100644
--- a/gns3server/modules/dynamips/nodes/ethernet_switch.py
+++ b/gns3server/modules/dynamips/nodes/ethernet_switch.py
@@ -20,8 +20,6 @@ Interface for Dynamips virtual Ethernet switch module ("ethsw").
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L558
 """
 
-
-from __future__ import unicode_literals
 from ..dynamips_error import DynamipsError
 
 import logging
diff --git a/gns3server/modules/dynamips/nodes/frame_relay_switch.py b/gns3server/modules/dynamips/nodes/frame_relay_switch.py
index 0c25c060..8a1eec31 100644
--- a/gns3server/modules/dynamips/nodes/frame_relay_switch.py
+++ b/gns3server/modules/dynamips/nodes/frame_relay_switch.py
@@ -20,7 +20,6 @@ Interface for Dynamips virtual Frame-Relay switch module.
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L642
 """
 
-from __future__ import unicode_literals
 from ..dynamips_error import DynamipsError
 
 import logging
diff --git a/gns3server/modules/dynamips/nodes/hub.py b/gns3server/modules/dynamips/nodes/hub.py
index 2d52fa7f..b66a5488 100644
--- a/gns3server/modules/dynamips/nodes/hub.py
+++ b/gns3server/modules/dynamips/nodes/hub.py
@@ -19,7 +19,6 @@
 Hub object that uses the Bridge interface to create a hub with ports.
 """
 
-from __future__ import unicode_literals
 from .bridge import Bridge
 from ..dynamips_error import DynamipsError
 
@@ -53,7 +52,6 @@ class Hub(Bridge):
                     break
                 name_id += 1
 
-        self._allocated_names.append(name)
         self._mapping = {}
         Bridge.__init__(self, hypervisor, name)
 
diff --git a/gns3server/modules/dynamips/nodes/router.py b/gns3server/modules/dynamips/nodes/router.py
index 7c5216ac..586144a4 100644
--- a/gns3server/modules/dynamips/nodes/router.py
+++ b/gns3server/modules/dynamips/nodes/router.py
@@ -20,7 +20,7 @@ Interface for Dynamips virtual Machine module ("vm")
 http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L77
 """
 
-from __future__ import unicode_literals
+from ..dynamips_hypervisor import DynamipsHypervisor
 from ..dynamips_error import DynamipsError
 import time
 import sys
@@ -68,6 +68,8 @@ class Router(object):
         self._name = '"' + name + '"'  # put name into quotes to protect spaces
         self._platform = platform
         self._image = ""
+        self._startup_config = ""
+        self._private_config = ""
         self._ram = 128  # Megabytes
         self._nvram = 128  # Kilobytes
         self._mmap = True
@@ -100,8 +102,12 @@ class Router(object):
             log.info("router {platform} {name} [id={id}] has been created".format(name=self._name,
                                                                                   platform=platform,
                                                                                   id=self._id))
-            self.console = self._hypervisor.baseconsole + self._id
-            self.aux = self._hypervisor.baseaux + self._id
+
+            # allocate and check that console and aux ports are unused
+            console_port = (self._hypervisor.baseconsole - 1) + self._id
+            self.console = DynamipsHypervisor.find_unused_port(console_port, console_port + 1, self._hypervisor.host)
+            aux_port = (self._hypervisor.baseaux - 1) + self._id
+            self.aux = DynamipsHypervisor.find_unused_port(aux_port, aux_port + 1, self._hypervisor.host)
 
             # get the default base MAC address
             self._mac_addr = self._hypervisor.send("{platform} get_mac_addr {name}".format(platform=self._platform,
@@ -130,6 +136,8 @@ class Router(object):
 
         router_defaults = {"platform": self._platform,
                            "image": self._image,
+                           "startup_config": self._startup_config,
+                           "private_config": self._private_config,
                            "ram": self._ram,
                            "nvram": self._nvram,
                            "mmap": self._mmap,
@@ -249,7 +257,7 @@ class Router(object):
         Deletes this router.
         """
 
-        self._hypervisor.send("vm delete {}".format(self._name))
+        self._hypervisor.send("vm clean_delete {}".format(self._name))
         self._hypervisor.devices.remove(self)
 
         log.info("router {name} [id={id}] has been deleted".format(name=self._name, id=self._id))
@@ -384,6 +392,46 @@ class Router(object):
 
         self._image = image
 
+    @property
+    def startup_config(self):
+        """
+        Returns the startup-config for this router.
+
+        :returns: path to startup-config file
+        """
+
+        return self._startup_config
+
+    @startup_config.setter
+    def startup_config(self, startup_config):
+        """
+        Sets the startup-config for this router.
+
+        :param startup_config: path to startup-config file
+        """
+
+        self._startup_config = startup_config
+
+    @property
+    def private_config(self):
+        """
+        Returns the private-config for this router.
+
+        :returns: path to private-config file
+        """
+
+        return self._private_config
+
+    @private_config.setter
+    def private_config(self, private_config):
+        """
+        Sets the private-config for this router.
+
+        :param private_config: path to private-config file
+        """
+
+        self._private_config = private_config
+
     def set_config(self, startup_config, private_config=''):
         """
         Sets the config files that are pushed to startup-config and
@@ -394,18 +442,20 @@ class Router(object):
         (keep existing data when if an empty string)
         """
 
-        self._hypervisor.send("vm set_config {name} {startup} {private}".format(name=self._name,
-                                                                                startup='"' + startup_config + '"',
-                                                                                private='"' + private_config + '"'))
+        if self._startup_config != startup_config or self._private_config != private_config:
 
-        log.info("router {name} [id={id}]: has a startup-config set: {startup}".format(name=self._name,
-                                                                                       id=self._id,
-                                                                                       startup='"' + startup_config + '"'))
+            self._hypervisor.send("vm set_config {name} {startup} {private}".format(name=self._name,
+                                                                                    startup='"' + startup_config + '"',
+                                                                                    private='"' + private_config + '"'))
 
-        if private_config:
-            log.info("router {name} [id={id}]: has a private-config set: {private}".format(name=self._name,
+            log.info("router {name} [id={id}]: has a startup-config set: {startup}".format(name=self._name,
                                                                                            id=self._id,
-                                                                                           private='"' + private_config + '"'))
+                                                                                           startup='"' + startup_config + '"'))
+
+            if private_config:
+                log.info("router {name} [id={id}]: has a private-config set: {private}".format(name=self._name,
+                                                                                               id=self._id,
+                                                                                               private='"' + private_config + '"'))
 
     def extract_config(self):
         """
diff --git a/gns3server/server.py b/gns3server/server.py
index 28e99882..219d671c 100644
--- a/gns3server/server.py
+++ b/gns3server/server.py
@@ -49,9 +49,16 @@ class Server(object):
         self._host = host
         self._port = port
         if ipc:
-            self._zmq_port = 0  # this forces module to use IPC for communications
+            self._zmq_port = 0  # this forces to use IPC for communications with the ZeroMQ server
         else:
-            self._zmq_port = port + 1  # this server port + 1
+            try:
+                # let the OS find an unused port for the ZeroMQ server
+                with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
+                    sock.bind(('127.0.0.1', 0))
+                    self._zmq_port = sock.getsockname()[1]
+            except socket.error as e:
+                log.warn("could not pick up a random port for the ZeroMQ server: {}".format(e))
+                self._zmq_port = port + 1  # let's try this server port + 1
         self._ipc = ipc
         self._modules = []
 
diff --git a/tests/dynamips/dynamips.stable b/tests/dynamips/dynamips.stable
index 72a01464..0af011ac 100755
Binary files a/tests/dynamips/dynamips.stable and b/tests/dynamips/dynamips.stable differ
diff --git a/tests/dynamips/test_hypervisor.py b/tests/dynamips/test_hypervisor.py
index d89da84e..ed0ee2ab 100644
--- a/tests/dynamips/test_hypervisor.py
+++ b/tests/dynamips/test_hypervisor.py
@@ -18,9 +18,9 @@ def test_host(hypervisor):
     assert hypervisor.host == "127.0.0.1"
 
 
-def test_workingdir(hypervisor):
+def test_working_dir(hypervisor):
 
-    assert hypervisor.workingdir == "/tmp"
+    assert hypervisor.working_dir == "/tmp"
 
 
 def test_path(hypervisor):
diff --git a/tox.ini b/tox.ini
index 8bfea5a7..84900ea9 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py27, py33
+envlist = py33
 
 [testenv]
 commands = py.test [] -s tests