--- a/src/tap-bridge/model/tap-bridge.cc	Tue Nov 19 06:50:18 2013 -0800
+++ b/src/tap-bridge/model/tap-bridge.cc	Tue Nov 19 06:52:02 2013 -0800
@@ -221,6 +221,9 @@
   //
   CreateTap ();
 
+  // Declare the link up
+  NotifyLinkUp ();
+
   //
   // Now spin up a read thread to read packets from the tap device.
   //
@@ -1056,18 +1059,29 @@
   return m_mtu;
 }
 
+void
+TapBridge::NotifyLinkUp (void)
+{
+  NS_LOG_FUNCTION_NOARGS ();
+  if (!m_linkUp)
+    {
+      m_linkUp = true;
+      m_linkChangeCallbacks ();
+    }
+}
 
 bool 
 TapBridge::IsLinkUp (void) const
 {
   NS_LOG_FUNCTION_NOARGS ();
-  return true;
+  return m_linkUp;
 }
 
 void 
 TapBridge::AddLinkChangeCallback (Callback<void> callback)
 {
   NS_LOG_FUNCTION_NOARGS ();
+  m_linkChangeCallbacks.ConnectWithoutContext (callback);
 }
 
 bool 

--- a/src/tap-bridge/model/tap-bridge.h	Tue Nov 19 06:50:18 2013 -0800
+++ b/src/tap-bridge/model/tap-bridge.h	Tue Nov 19 06:52:02 2013 -0800
@@ -291,6 +291,8 @@
    */
   Ptr<Packet> Filter (Ptr<Packet> packet, Address *src, Address *dst, uint16_t *type);
 
+  void NotifyLinkUp (void);
+
   /**
    * \internal
    *
@@ -463,6 +465,22 @@
    * multithreaded apps is not a good thing.
    */
   uint32_t m_nodeId;
+
+  /**
+   * \internal
+   *
+   * Flag indicating whether or not the link is up.  In this case,
+   * whether or not ns-3 is connected to the underlying TAP device
+   * with a file descriptor.
+   */
+  bool m_linkUp;
+
+  /**
+   * \internal
+   *
+   * Callbacks to fire if the link changes state (up or down).
+   */
+  TracedCallback<> m_linkChangeCallbacks;
 };
 
 } // namespace ns3