improved CLI
diff --git a/emuvim/dcemulator/net.py b/emuvim/dcemulator/net.py
index 1762e0b..83ac619 100644
--- a/emuvim/dcemulator/net.py
+++ b/emuvim/dcemulator/net.py
@@ -114,6 +114,15 @@
     def getNextIp(self):
         return self.mnet.getNextIp()
 
+    def getAllContainers(self):
+        """
+        Returns a list with all containers within all data centers.
+        """
+        all_containers = []
+        for dc in self.dcs.itervalues():
+            all_containers += dc.listCompute()
+        return all_containers
+
     def start(self):
         # start
         for dc in self.dcs.itervalues():
diff --git a/emuvim/dcemulator/node.py b/emuvim/dcemulator/node.py
index 0d96033..de64d69 100644
--- a/emuvim/dcemulator/node.py
+++ b/emuvim/dcemulator/node.py
@@ -100,7 +100,7 @@
         """
         assert name is not None
         # no duplications
-        if name in self.containers:
+        if name in [c.name for c in self.net.getAllContainers()]:
             raise Exception("Container with name %s already exists." % name)
         # set default parameter
         if image is None: