diff -r c009d3d36e85 examples/simple-p2p.cc
--- a/examples/simple-p2p.cc	Wed Jun 13 18:40:38 2007 +0100
+++ b/examples/simple-p2p.cc	Wed Jun 13 19:20:00 2007 +0100
@@ -164,6 +164,18 @@ int main (int argc, char *argv[])
   ooff->Start(Seconds(1.1));
   ooff->Stop (Seconds(10.0));
 
+  // Create a 3rd flow from n3 to <brodcast>, starting at time 1.1 seconds
+  ooff = Create<OnOffApplication> (
+    n3, 
+    Ipv4Address("255.255.255.255"), 
+    80, 
+    "Udp",
+    ConstantVariable(1), 
+    ConstantVariable(0));
+  // Start the application
+  ooff->Start(Seconds(1.1));
+  ooff->Stop (Seconds(10.0));
+
   // Here, finish off packet routing configuration
   // This will likely set by some global StaticRouting object in the future
   Ptr<Ipv4> ipv4;
diff -r c009d3d36e85 src/internet-node/arp-cache.cc
--- a/src/internet-node/arp-cache.cc	Wed Jun 13 18:40:38 2007 +0100
+++ b/src/internet-node/arp-cache.cc	Wed Jun 13 18:52:06 2007 +0100
@@ -109,6 +109,8 @@ ArpCache::Entry *
 ArpCache::Entry *
 ArpCache::Add (Ipv4Address to)
 {
+  NS_ASSERT (m_arpCache.find (to) == m_arpCache.end ());
+
   ArpCache::Entry *entry = new ArpCache::Entry (this);
   m_arpCache[to] = entry;  
   return entry;
diff -r c009d3d36e85 src/internet-node/arp-ipv4-interface.cc
--- a/src/internet-node/arp-ipv4-interface.cc	Wed Jun 13 18:40:38 2007 +0100
+++ b/src/internet-node/arp-ipv4-interface.cc	Wed Jun 13 18:52:06 2007 +0100
@@ -21,6 +21,7 @@
  */
 
 #include "ns3/packet.h"
+#include "ns3/debug.h"
 #include "ns3/composite-trace-resolver.h"
 #include "ns3/node.h"
 #include "ns3/net-device.h"
@@ -60,7 +61,19 @@ ArpIpv4Interface::SendTo (Packet p, Ipv4
     {
       Ptr<ArpPrivate> arp = m_node->QueryInterface<ArpPrivate> (ArpPrivate::iid);
       MacAddress hardwareDestination;
-      bool found = arp->Lookup (p, dest, GetDevice (), &hardwareDestination);
+      bool found;
+
+      if (dest.IsBroadcast ())
+        {
+           hardwareDestination = GetDevice ()->GetBroadcast ();
+           found = true;
+        }
+      else
+        {
+          Ptr<ArpPrivate> arp = m_node->QueryInterface<ArpPrivate> (ArpPrivate::iid);
+          found = arp->Lookup (p, dest, GetDevice (), &hardwareDestination);
+        }
+
       if (found)
         {
           GetDevice ()->Send (p, hardwareDestination, Ipv4L3Protocol::PROT_NUMBER);
diff -r c009d3d36e85 src/internet-node/arp-l3-protocol.cc
--- a/src/internet-node/arp-l3-protocol.cc	Wed Jun 13 18:40:38 2007 +0100
+++ b/src/internet-node/arp-l3-protocol.cc	Wed Jun 13 18:52:06 2007 +0100
@@ -87,6 +87,13 @@ ArpL3Protocol::Receive(Packet& packet, P
   ArpCache *cache = FindCache (device);
   ArpHeader arp;
   packet.RemoveHeader (arp);
+  
+  NS_DEBUG ("ARP: received "<< (arp.IsRequest ()? "request" : "reply") <<
+            " node="<<m_node->GetId ()<<", got request from " <<
+            arp.GetSourceIpv4Address () << " for address " <<
+            arp.GetDestinationIpv4Address () << "; we have address " <<
+            cache->GetInterface ()->GetAddress ());
+
   if (arp.IsRequest () && 
       arp.GetDestinationIpv4Address () == cache->GetInterface ()->GetAddress ()) 
     {
@@ -128,6 +135,12 @@ ArpL3Protocol::Receive(Packet& packet, P
 	  // XXX report packet as dropped.
         }
     }
+  else
+    {
+      NS_DEBUG ("node="<<m_node->GetId ()<<", got request from " <<
+                arp.GetSourceIpv4Address () << " for unknown address " <<
+                arp.GetDestinationIpv4Address () << " -- drop");
+    }
 }
 bool 
 ArpL3Protocol::Lookup (Packet &packet, Ipv4Address destination, 
@@ -203,6 +216,11 @@ ArpL3Protocol::SendArpRequest (ArpCache 
 ArpL3Protocol::SendArpRequest (ArpCache const *cache, Ipv4Address to)
 {
   ArpHeader arp;
+  NS_DEBUG ("ARP: sending request from node "<<m_node->GetId ()<<
+            " || src: " << cache->GetDevice ()->GetAddress () <<
+            " / " << cache->GetInterface ()->GetAddress () <<
+            " || dst: " << cache->GetDevice ()->GetBroadcast () <<
+            " / " << to);
   arp.SetRequest (cache->GetDevice ()->GetAddress (),
 		  cache->GetInterface ()->GetAddress (), 
                   cache->GetDevice ()->GetBroadcast (),
@@ -216,6 +234,10 @@ ArpL3Protocol::SendArpReply (ArpCache co
 ArpL3Protocol::SendArpReply (ArpCache const *cache, Ipv4Address toIp, MacAddress toMac)
 {
   ArpHeader arp;
+  NS_DEBUG ("ARP: sending reply from node "<<m_node->GetId ()<<
+            "|| src: " << cache->GetDevice ()->GetAddress () << 
+            " / " << cache->GetInterface ()->GetAddress () <<
+            " || dst: " << toMac << " / " << toIp);
   arp.SetReply (cache->GetDevice ()->GetAddress (),
                 cache->GetInterface ()->GetAddress (),
                 toMac, toIp);
diff -r c009d3d36e85 src/internet-node/ipv4-l3-protocol.cc
--- a/src/internet-node/ipv4-l3-protocol.cc	Wed Jun 13 18:40:38 2007 +0100
+++ b/src/internet-node/ipv4-l3-protocol.cc	Wed Jun 13 18:52:06 2007 +0100
@@ -404,23 +404,39 @@ Ipv4L3Protocol::Send (Packet const &pack
 
   m_identification ++;
 
-  // XXX Note here that in most ipv4 stacks in the world,
-  // the route calculation for an outgoing packet is not
-  // done in the ip layer. It is done within the application
-  // socket when the first packet is sent to avoid this
-  // costly lookup on a per-packet basis.
-  // That would require us to get the route from the packet,
-  // most likely with a packet tag. The higher layers do not
-  // do this yet for us.
-  Ipv4Route *route = Lookup (ipHeader.GetDestination ());
-  if (route == 0) 
-    {
-      NS_DEBUG ("not for me -- forwarding but no route to host. drop.");
-      m_dropTrace (packet);
-      return;
-    }
-
-  SendRealOut (packet, ipHeader, *route);
+  if (destination.IsBroadcast ())
+    {
+      Packet packet1 = packet;
+      packet1.AddHeader (ipHeader);
+
+      for (Ipv4InterfaceList::iterator ifaceIter = m_interfaces.begin ();
+           ifaceIter != m_interfaces.end (); ifaceIter++)
+        {
+          Ipv4Interface *outInterface = *ifaceIter;
+          // XXX log trace here.
+          NS_ASSERT (packet.GetSize () <= outInterface->GetMtu ());
+          outInterface->Send (packet1, destination);
+        }
+    }
+  else
+    {
+      // XXX Note here that in most ipv4 stacks in the world,
+      // the route calculation for an outgoing packet is not
+      // done in the ip layer. It is done within the application
+      // socket when the first packet is sent to avoid this
+      // costly lookup on a per-packet basis.
+      // That would require us to get the route from the packet,
+      // most likely with a packet tag. The higher layers do not
+      // do this yet for us.
+      Ipv4Route *route = Lookup (ipHeader.GetDestination ());
+      if (route == 0) 
+        {
+          NS_DEBUG ("not for me -- forwarding but no route to host. drop.");
+          m_dropTrace (packet);
+          return;
+        }
+      SendRealOut (packet, ipHeader, *route);
+    }
 }
 
 void
@@ -470,7 +486,7 @@ Ipv4L3Protocol::Forwarding (Packet const
 	}
     }
       
-  if (ipHeader.GetDestination ().IsEqual (Ipv4Address::GetBroadcast ())) 
+  if (ipHeader.GetDestination ().IsBroadcast ()) 
     {
       NS_DEBUG ("for me 3");
       return false;
diff -r c009d3d36e85 src/node/ipv4-address.cc
--- a/src/node/ipv4-address.cc	Wed Jun 13 18:40:38 2007 +0100
+++ b/src/node/ipv4-address.cc	Wed Jun 13 19:02:38 2007 +0100
@@ -145,6 +145,18 @@ Ipv4Address::IsEqual (Ipv4Address other)
   }
 }
 
+bool
+Ipv4Address::IsBroadcast (void) const
+{
+  return (m_address == 0xffffffffU);
+}
+
+Ipv4Address
+Ipv4Address::CombineMask (Ipv4Mask const &mask) const
+{
+  return Ipv4Address (GetHostOrder () & mask.GetHostOrder ());
+}
+
 bool 
 Ipv4Address::IsMulticast (void)
 {
diff -r c009d3d36e85 src/node/ipv4-address.h
--- a/src/node/ipv4-address.h	Wed Jun 13 18:40:38 2007 +0100
+++ b/src/node/ipv4-address.h	Wed Jun 13 19:05:51 2007 +0100
@@ -26,6 +26,8 @@
 #include <ostream>
 
 namespace ns3 {
+
+class Ipv4Mask;
 
 /** Ipv4 addresses are stored in host order in
   * this class.
@@ -80,8 +82,19 @@ public:
    */
   void Print (std::ostream &os) const;
 
-  bool IsBroadcast (void);
+  bool IsBroadcast (void) const;
   bool IsMulticast (void);
+  
+  /**
+   * \brief Combine this address with a network mask
+   *
+   * This method returns an IPv4 address that is this address combined
+   * (bitwise and) with a network mask, yielding an IPv4 network
+   * address.
+   *
+   * \param a network mask 
+   */
+  Ipv4Address CombineMask (Ipv4Mask const &mask) const;
 
   static Ipv4Address GetZero (void);
   static Ipv4Address GetAny (void);