diff -r 6cd5056a8fe0 src/devices/bridge/bridge-net-device.cc
--- a/src/devices/bridge/bridge-net-device.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/bridge/bridge-net-device.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -317,7 +317,7 @@
 
 
 void 
-BridgeNetDevice::SetLinkChangeCallback (Callback<void> callback)
+BridgeNetDevice::AddLinkChangeCallback (Callback<void> callback)
 {}
 
 
diff -r 6cd5056a8fe0 src/devices/bridge/bridge-net-device.h
--- a/src/devices/bridge/bridge-net-device.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/bridge/bridge-net-device.h	Mon Jul 27 17:56:54 2009 +0200
@@ -96,7 +96,7 @@
   virtual bool SetMtu (const uint16_t mtu);
   virtual uint16_t GetMtu (void) const;
   virtual bool IsLinkUp (void) const;
-  virtual void SetLinkChangeCallback (Callback<void> callback);
+  virtual void AddLinkChangeCallback (Callback<void> callback);
   virtual bool IsBroadcast (void) const;
   virtual Address GetBroadcast (void) const;
   virtual bool IsMulticast (void) const;
diff -r 6cd5056a8fe0 src/devices/csma/csma-net-device.cc
--- a/src/devices/csma/csma-net-device.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/csma/csma-net-device.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -841,10 +841,14 @@
   NS_LOG_FUNCTION_NOARGS ();
 
   m_linkUp = true;
-  if (m_linkChangeCallback.IsNull () == false)
-    {
-      m_linkChangeCallback ();
-    }
+  for (std::list<Callback<void> >::const_iterator it = m_linkChangeCallbacks.begin () ; 
+      it != m_linkChangeCallbacks.end () ; ++it)
+  {
+    if ((*it).IsNull () == false)
+      {
+        (*it) ();
+      }
+  }
 }
 
   void 
@@ -890,10 +894,10 @@
 }
 
   void 
-CsmaNetDevice::SetLinkChangeCallback (Callback<void> callback)
+CsmaNetDevice::AddLinkChangeCallback (Callback<void> callback)
 {
   NS_LOG_FUNCTION (&callback);
-  m_linkChangeCallback = callback;
+  m_linkChangeCallbacks.push_back (callback);
 }
 
   bool 
diff -r 6cd5056a8fe0 src/devices/csma/csma-net-device.h
--- a/src/devices/csma/csma-net-device.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/csma/csma-net-device.h	Mon Jul 27 17:56:54 2009 +0200
@@ -22,6 +22,7 @@
 #define CSMA_NET_DEVICE_H
 
 #include <string.h>
+#include <list>
 #include "ns3/node.h"
 #include "ns3/backoff.h"
 #include "ns3/address.h"
@@ -306,7 +307,7 @@
   virtual void SetAddress (Address address);
   virtual Address GetAddress (void) const;
   virtual bool IsLinkUp (void) const;
-  virtual void SetLinkChangeCallback (Callback<void> callback);
+  virtual void AddLinkChangeCallback (Callback<void> callback);
   virtual bool IsBroadcast (void) const;
   virtual Address GetBroadcast (void) const;
   virtual bool IsMulticast (void) const;
@@ -808,7 +809,7 @@
   /**
    * Callback to fire if the link changes state (up or down).
    */
-  Callback<void> m_linkChangeCallback;
+  std::list<Callback<void> > m_linkChangeCallbacks;
 
   static const uint16_t DEFAULT_FRAME_SIZE = 1518;
   static const uint16_t ETHERNET_OVERHEAD = 18;
diff -r 6cd5056a8fe0 src/devices/emu/emu-net-device.cc
--- a/src/devices/emu/emu-net-device.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/emu/emu-net-device.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -869,10 +869,14 @@
 EmuNetDevice::NotifyLinkUp (void)
 {
   m_linkUp = true;
-  if (!m_linkChangeCallback.IsNull ())
-    {
-      m_linkChangeCallback ();
-    }
+  for (std::list<Callback<void> >::const_iterator it = m_linkChangeCallbacks.begin () ;
+      it != m_linkChangeCallbacks.end () ; ++it)
+  {
+    if ((*it).IsNull () == false)
+      {
+        (*it) ();
+      }
+  }
 }
 
 void 
@@ -943,9 +947,9 @@
 }
 
 void 
-EmuNetDevice::SetLinkChangeCallback (Callback<void> callback)
+EmuNetDevice::AddLinkChangeCallback (Callback<void> callback)
 {
-  m_linkChangeCallback = callback;
+  m_linkChangeCallbacks.push_back (callback);
 }
 
 bool 
diff -r 6cd5056a8fe0 src/devices/emu/emu-net-device.h
--- a/src/devices/emu/emu-net-device.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/emu/emu-net-device.h	Mon Jul 27 17:56:54 2009 +0200
@@ -20,6 +20,7 @@
 #define EMU_NET_DEVICE_H
 
 #include <string.h>
+#include <list>
 #include "ns3/address.h"
 #include "ns3/net-device.h"
 #include "ns3/node.h"
@@ -110,7 +111,7 @@
 
   virtual bool IsLinkUp (void) const;
 
-  virtual void SetLinkChangeCallback (Callback<void> callback);
+  virtual void AddLinkChangeCallback (Callback<void> callback);
 
   virtual bool IsBroadcast (void) const;
   virtual Address GetBroadcast (void) const;
@@ -461,7 +462,7 @@
   /**
    * Callback to fire if the link changes state (up or down).
    */
-  Callback<void> m_linkChangeCallback;
+  std::list<Callback<void> > m_linkChangeCallbacks;
 
   /**
    * The unix/linux name of the underlying device (e.g., eth0)
diff -r 6cd5056a8fe0 src/devices/point-to-point/point-to-point-net-device.cc
--- a/src/devices/point-to-point/point-to-point-net-device.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/point-to-point/point-to-point-net-device.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -366,10 +366,14 @@
 PointToPointNetDevice::NotifyLinkUp (void)
 {
   m_linkUp = true;
-  if (!m_linkChangeCallback.IsNull ())
-    {
-      m_linkChangeCallback ();
-    }
+  for (std::list<Callback<void> >::const_iterator it = m_linkChangeCallbacks.begin () ;
+        it != m_linkChangeCallbacks.end () ; ++it)
+  {
+    if (!(*it).IsNull ())
+      {
+        (*it) ();
+      }
+  }
 }
 
   void 
@@ -415,9 +419,9 @@
 }
 
   void 
-PointToPointNetDevice::SetLinkChangeCallback (Callback<void> callback)
+PointToPointNetDevice::AddLinkChangeCallback (Callback<void> callback)
 {
-  m_linkChangeCallback = callback;
+  m_linkChangeCallbacks.push_back (callback);
 }
 
 //
diff -r 6cd5056a8fe0 src/devices/point-to-point/point-to-point-net-device.h
--- a/src/devices/point-to-point/point-to-point-net-device.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/point-to-point/point-to-point-net-device.h	Mon Jul 27 17:56:54 2009 +0200
@@ -20,6 +20,7 @@
 #define POINT_TO_POINT_NET_DEVICE_H
 
 #include <string.h>
+#include <list>
 #include "ns3/address.h"
 #include "ns3/node.h"
 #include "ns3/net-device.h"
@@ -231,7 +232,7 @@
 
   virtual bool IsLinkUp (void) const;
 
-  virtual void SetLinkChangeCallback (Callback<void> callback);
+  virtual void AddLinkChangeCallback (Callback<void> callback);
 
   virtual bool IsBroadcast (void) const;
   virtual Address GetBroadcast (void) const;
@@ -520,7 +521,7 @@
   NetDevice::PromiscReceiveCallback m_promiscCallback;
   uint32_t m_ifIndex;
   bool m_linkUp;
-  Callback<void> m_linkChangeCallback;
+  std::list<Callback<void> > m_linkChangeCallbacks;
 
   static const uint16_t DEFAULT_MTU = 1500;
   static const uint16_t PPP_OVERHEAD = 2;
diff -r 6cd5056a8fe0 src/devices/tap-bridge/tap-bridge.cc
--- a/src/devices/tap-bridge/tap-bridge.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/tap-bridge/tap-bridge.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -1026,7 +1026,7 @@
 }
 
 void 
-TapBridge::SetLinkChangeCallback (Callback<void> callback)
+TapBridge::AddLinkChangeCallback (Callback<void> callback)
 {
   NS_LOG_FUNCTION_NOARGS ();
 }
diff -r 6cd5056a8fe0 src/devices/tap-bridge/tap-bridge.h
--- a/src/devices/tap-bridge/tap-bridge.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/tap-bridge/tap-bridge.h	Mon Jul 27 17:56:54 2009 +0200
@@ -181,7 +181,7 @@
   virtual bool SetMtu (const uint16_t mtu);
   virtual uint16_t GetMtu (void) const;
   virtual bool IsLinkUp (void) const;
-  virtual void SetLinkChangeCallback (Callback<void> callback);
+  virtual void AddLinkChangeCallback (Callback<void> callback);
   virtual bool IsBroadcast (void) const;
   virtual Address GetBroadcast (void) const;
   virtual bool IsMulticast (void) const;
diff -r 6cd5056a8fe0 src/devices/virtual-net-device/virtual-net-device.cc
--- a/src/devices/virtual-net-device/virtual-net-device.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/virtual-net-device/virtual-net-device.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -194,7 +194,7 @@
 }
 
 void
-VirtualNetDevice::SetLinkChangeCallback (Callback<void> callback)
+VirtualNetDevice::AddLinkChangeCallback (Callback<void> callback)
 {
 }
 
diff -r 6cd5056a8fe0 src/devices/virtual-net-device/virtual-net-device.h
--- a/src/devices/virtual-net-device/virtual-net-device.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/virtual-net-device/virtual-net-device.h	Mon Jul 27 17:56:54 2009 +0200
@@ -122,7 +122,7 @@
   virtual Address GetAddress (void) const;
   virtual uint16_t GetMtu (void) const;
   virtual bool IsLinkUp (void) const;
-  virtual void SetLinkChangeCallback (Callback<void> callback);
+  virtual void AddLinkChangeCallback (Callback<void> callback);
   virtual bool IsBroadcast (void) const;
   virtual Address GetBroadcast (void) const;
   virtual bool IsMulticast (void) const;
diff -r 6cd5056a8fe0 src/devices/wifi/wifi-net-device.cc
--- a/src/devices/wifi/wifi-net-device.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/wifi/wifi-net-device.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -196,9 +196,9 @@
   return m_phy != 0 && m_linkUp;
 }
 void 
-WifiNetDevice::SetLinkChangeCallback (Callback<void> callback)
+WifiNetDevice::AddLinkChangeCallback (Callback<void> callback)
 {
-  m_linkChange = callback;
+  m_linkChanges.push_back (callback);
 }
 bool 
 WifiNetDevice::IsBroadcast (void) const
@@ -312,19 +312,27 @@
 WifiNetDevice::LinkUp (void)
 {
   m_linkUp = true;
-  if (!m_linkChange.IsNull ())
-    {
-      m_linkChange ();
-    }
+  for (std::list<Callback<void> >::const_iterator it = m_linkChanges.begin () ;
+        it != m_linkChanges.end () ; ++it)
+  {
+    if (!(*it).IsNull ())
+      {
+        (*it) ();
+      }
+  }
 }
 void
 WifiNetDevice::LinkDown (void)
 {
   m_linkUp = false;
-  if (!m_linkChange.IsNull ())
-    {
-      m_linkChange ();
-    }
+  for (std::list<Callback<void> >::const_iterator it = m_linkChanges.begin () ;
+        it != m_linkChanges.end () ; ++it)
+  {
+    if (!(*it).IsNull ())
+      {
+        (*it) ();
+      }
+  }
 }
 
 bool
diff -r 6cd5056a8fe0 src/devices/wifi/wifi-net-device.h
--- a/src/devices/wifi/wifi-net-device.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/devices/wifi/wifi-net-device.h	Mon Jul 27 17:56:54 2009 +0200
@@ -27,6 +27,7 @@
 #include "ns3/mac48-address.h"
 #include "wifi-remote-station-manager.h"
 #include <string>
+#include <list>
 
 namespace ns3 {
 
@@ -83,7 +84,7 @@
   virtual bool SetMtu (const uint16_t mtu);
   virtual uint16_t GetMtu (void) const;
   virtual bool IsLinkUp (void) const;
-  virtual void SetLinkChangeCallback (Callback<void> callback);
+  virtual void AddLinkChangeCallback (Callback<void> callback);
   virtual bool IsBroadcast (void) const;
   virtual Address GetBroadcast (void) const;
   virtual bool IsMulticast (void) const;
@@ -123,7 +124,7 @@
 
   uint32_t m_ifIndex;
   bool m_linkUp;
-  Callback<void> m_linkChange;
+  std::list<Callback<void> > m_linkChanges;
   mutable uint16_t m_mtu;
   bool m_configComplete;
 };
diff -r 6cd5056a8fe0 src/internet-stack/arp-l3-protocol.cc
--- a/src/internet-stack/arp-l3-protocol.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/internet-stack/arp-l3-protocol.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -116,7 +116,7 @@
   Ptr<ArpCache> cache = CreateObject<ArpCache> ();
   cache->SetDevice (device, interface);
   NS_ASSERT (device->IsBroadcast ());
-  device->SetLinkChangeCallback (MakeCallback (&ArpCache::Flush, cache));
+  device->AddLinkChangeCallback (MakeCallback (&ArpCache::Flush, cache));
   cache->SetArpRequestCallback (MakeCallback (&ArpL3Protocol::SendArpRequest, this));
   m_cacheList.push_back (cache);
   return cache;
diff -r 6cd5056a8fe0 src/internet-stack/loopback-net-device.cc
--- a/src/internet-stack/loopback-net-device.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/internet-stack/loopback-net-device.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -125,7 +125,7 @@
 }
 
 void 
-LoopbackNetDevice::SetLinkChangeCallback (Callback<void> callback)
+LoopbackNetDevice::AddLinkChangeCallback (Callback<void> callback)
 {}
 
 bool 
diff -r 6cd5056a8fe0 src/internet-stack/loopback-net-device.h
--- a/src/internet-stack/loopback-net-device.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/internet-stack/loopback-net-device.h	Mon Jul 27 17:56:54 2009 +0200
@@ -50,7 +50,7 @@
   virtual bool SetMtu (const uint16_t mtu);
   virtual uint16_t GetMtu (void) const;
   virtual bool IsLinkUp (void) const;
-  virtual void SetLinkChangeCallback (Callback<void> callback);
+  virtual void AddLinkChangeCallback (Callback<void> callback);
   virtual bool IsBroadcast (void) const;
   virtual Address GetBroadcast (void) const;
   virtual bool IsMulticast (void) const;
diff -r 6cd5056a8fe0 src/node/net-device.h
--- a/src/node/net-device.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/node/net-device.h	Mon Jul 27 17:56:54 2009 +0200
@@ -128,12 +128,12 @@
   /**
    * \param callback the callback to invoke
    *
-   * Register a callback invoked whenever the link 
+   * Add a callback invoked whenever the link 
    * status changes to UP. This callback is typically used
-   * by the IP/ARP layer to flush the ARP cache 
-   * whenever the link goes up.
+   * by the IP/ARP layer to flush the ARP cache and by IPv6 stack
+   * to flush NDISC cache whenever the link goes up.
    */
-  virtual void SetLinkChangeCallback (Callback<void> callback) = 0;
+  virtual void AddLinkChangeCallback (Callback<void> callback) = 0;
   /**
    * \return true if this interface supports a broadcast address,
    *         false otherwise.
diff -r 6cd5056a8fe0 src/node/simple-net-device.cc
--- a/src/node/simple-net-device.cc	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/node/simple-net-device.cc	Mon Jul 27 17:56:54 2009 +0200
@@ -121,7 +121,7 @@
   return true;
 }
 void 
-SimpleNetDevice::SetLinkChangeCallback (Callback<void> callback)
+SimpleNetDevice::AddLinkChangeCallback (Callback<void> callback)
 {}
 bool 
 SimpleNetDevice::IsBroadcast (void) const
diff -r 6cd5056a8fe0 src/node/simple-net-device.h
--- a/src/node/simple-net-device.h	Sun Jul 26 07:25:19 2009 -0700
+++ b/src/node/simple-net-device.h	Mon Jul 27 17:56:54 2009 +0200
@@ -53,7 +53,7 @@
   virtual bool SetMtu (const uint16_t mtu);
   virtual uint16_t GetMtu (void) const;
   virtual bool IsLinkUp (void) const;
-  virtual void SetLinkChangeCallback (Callback<void> callback);
+  virtual void AddLinkChangeCallback (Callback<void> callback);
   virtual bool IsBroadcast (void) const;
   virtual Address GetBroadcast (void) const;
   virtual bool IsMulticast (void) const;