diff --git a/bin/mn b/bin/mn
index 91a6369..f6b9e78 100755
--- a/bin/mn
+++ b/bin/mn
@@ -48,7 +48,7 @@ HOSTS = { 'proc': Host,
           'rt': custom( CPULimitedHost, sched='rt' ),
           'cfs': custom( CPULimitedHost, sched='cfs' ) }
 
-CONTROLLERDEF = 'ref'
+CONTROLLERDEF = 'ovsc'
 CONTROLLERS = { 'ref': Controller,
                 'ovsc': OVSController,
                 'nox': NOX,
diff --git a/debian/control b/debian/control
index 152d22a..649c234 100644
--- a/debian/control
+++ b/debian/control
@@ -13,6 +13,8 @@ Package: mininet
 Architecture: any
 Depends:
   openvswitch-switch,
+  openvswitch-controller,
+  telnet,
   ${misc:Depends},
   ${python:Depends},
   ${shlibs:Depends}
diff --git a/mininet/node.py b/mininet/node.py
index 6db75c6..8e4786d 100644
--- a/mininet/node.py
+++ b/mininet/node.py
@@ -975,6 +975,20 @@ class Controller( Node ):
         self.port = port
         Node.__init__( self, name, inNamespace=inNamespace,
             ip=ip, **params  )
+        self.cmd( 'ifconfig lo up' )  # Shouldn't be necessary
+        self.checkListening()
+
+    def checkListening( self ):
+        "Make sure no controllers are running on our port"
+        listening = self.cmd( "echo A | telnet -e A %s %d" %
+                              ( self.ip, self.port ) )
+        if 'Unable' not in listening:
+            servers = self.cmd( 'netstat -atp' ).split( '\n' )
+            pstr = ':%d ' % self.port
+            info = servers[ 0:1 ] + [ s for s in servers if pstr in s ]
+            raise Exception( "Please shut down the controller which is"
+                             " running on port %d:\n" % self.port +
+                             '\n'.join( info ) )
 
     def start( self ):
         """Start <controller> <args> on controller.