make sure the MTU is correcrtly setup and the link is up.

src/node/p2p-net-device.cc

@@ -28,8 +28,12 @@
 namespace ns3 {
 
 P2PNetDevice::P2PNetDevice (Node *node, MacAddress const &addr)
-  : NetDevice (node, addr)
-{}
+  : NetDevice (node, addr),
+    m_rate (500)
+{
+  SetMtu (2300);
+  EnableBroadcast (MacAddress ("ff:ff:ff:ff:ff:ff"));
+}
 
 P2PNetDevice::~P2PNetDevice()
 { // Inform channel that we are destroyed
@@ -46,6 +50,7 @@ void
 P2PNetDevice::Connect (P2PChannel *channel)
 {
   m_channel = channel;
+  NotifyLinkUp ();
 }
 
 bool