diff -r a3ef4e9615c0 src/internet/model/arp-cache.cc
--- a/src/internet/model/arp-cache.cc	Sun Sep 13 08:41:50 2015 -0700
+++ b/src/internet/model/arp-cache.cc	Sun Sep 13 19:13:02 2015 -0700
@@ -99,7 +99,16 @@
 ArpCache::DoDispose (void)
 {
   NS_LOG_FUNCTION (this);
-  Flush ();
+  for (CacheI i = m_arpCache.begin (); i != m_arpCache.end (); i++)
+    {
+      delete (*i).second;
+    }
+  m_arpCache.erase (m_arpCache.begin (), m_arpCache.end ());
+  if (m_waitReplyTimer.IsRunning ())
+    {
+      NS_LOG_LOGIC ("Stopping WaitReplyTimer at " << Simulator::Now ().GetSeconds () << " due to ArpCache flush");
+      m_waitReplyTimer.Cancel ();
+    }
   m_device = 0;
   m_interface = 0;
   if (!m_waitReplyTimer.IsRunning ())
@@ -241,11 +250,22 @@
 ArpCache::Flush (void)
 {
   NS_LOG_FUNCTION (this);
+  std::vector<Ipv4Address> keysToErase;
+  // First delete the entry
   for (CacheI i = m_arpCache.begin (); i != m_arpCache.end (); i++) 
     {
-      delete (*i).second;
+      if (!(*i).second->IsPermanent ())
+         {
+            delete (*i).second;
+            keysToErase.push_back ((*i).first);
+         }
     }
-  m_arpCache.erase (m_arpCache.begin (), m_arpCache.end ());
+  // Now erase the entries from the cache.  Doing it outside of the above 
+  // for loop since erasing invalidates the iterator
+  for(std::vector<Ipv4Address>::size_type i = 0; i != keysToErase.size(); i++) 
+    {
+      m_arpCache.erase (keysToErase[i]);
+    }
   if (m_waitReplyTimer.IsRunning ())
     {
       NS_LOG_LOGIC ("Stopping WaitReplyTimer at " << Simulator::Now ().GetSeconds () << " due to ArpCache flush");
@@ -388,7 +408,7 @@
 void
 ArpCache::Entry::MarkPermanent (Address macAddress)
 {
-  NS_LOG_FUNCTION (this);
+  NS_LOG_FUNCTION (this << macAddress);
   m_macAddress = macAddress;
   m_state = PERMANENT;
   ClearRetries ();