diff --git a/machines/models.py b/machines/models.py
index 0313470d..cb859141 100644
--- a/machines/models.py
+++ b/machines/models.py
@@ -280,13 +280,13 @@ class Interface(models.Model):
         return str(domain)
 
     def has_private_ip(self):
-        if hasattr(self, 'ipv4'):
+        if self.ipv4:
             return IPAddress(str(self.ipv4)).is_private()
         else:
             return False
 
     def may_have_port_open(self):
-        return hasattr(self, 'ipv4') and self.has_private_ip()
+        return self.ipv4 and not self.has_private_ip()
 
 class Domain(models.Model):
     PRETTY_NAME = "Domaine dns"
@@ -497,7 +497,7 @@ def interface_post_save(sender, **kwargs):
     interface = kwargs['instance']
     user = interface.machine.user
     user.ldap_sync(base=False, access_refresh=False, mac_refresh=True)
-    if interface.may_have_port_open() and interface.port_lists.all():
+    if not interface.may_have_port_open() and interface.port_lists.all():
         interface.port_lists.clear()
     # Regen services
     regen('dhcp')
diff --git a/machines/templates/machines/aff_machines.html b/machines/templates/machines/aff_machines.html
index c4a2dd56..6cf306f7 100644
--- a/machines/templates/machines/aff_machines.html
+++ b/machines/templates/machines/aff_machines.html
@@ -91,11 +91,13 @@ with this program; if not, write to the Free Software Foundation, Inc.,
                                 <i class="glyphicon glyphicon-edit"></i> Gerer les alias
                             </a>
                         </li>
+			{% if interface.may_have_port_open %}
 			<li>
 			    <a href="{% url 'machines:port-config' interface.id%}">
                                 <i class="glyphicon glyphicon-edit"></i> Gerer la configuration des ports
 			    </a>
 			</li>
+			{% endif %}
 			<li>
                             <a href="{% url 'machines:history' 'interface' interface.id %}">
                                 <i class="glyphicon glyphicon-time"></i> Historique
diff --git a/machines/views.py b/machines/views.py
index 8a01d813..8200843c 100644
--- a/machines/views.py
+++ b/machines/views.py
@@ -1001,6 +1001,9 @@ def configure_ports(request, pk):
     except Interface.DoesNotExist:
         messages.error(request, u"Interface inexistante" )
         return redirect("/machines")
+    if not interface_instance.may_have_port_open():
+        messages.error(request, "L'ip de cette interface n'est pas publique ou non assignée")
+        return redirect("/machines")
     interface = EditOuverturePortConfigForm(request.POST or None, instance=interface_instance)
     if interface.is_valid():
         interface.save()