diff --git a/ns-3.10/src/internet-stack/ipv4-l3-protocol.cc b/ns-3.10/src/internet-stack/ipv4-l3-protocol.cc
index eefcbb5..dc9c48d 100644
--- a/ns-3.10/src/internet-stack/ipv4-l3-protocol.cc
+++ b/ns-3.10/src/internet-stack/ipv4-l3-protocol.cc
@@ -739,30 +739,32 @@ Ipv4L3Protocol::IpMulticastForward (Ptr<Ipv4MulticastRoute> mrtentry, Ptr<const
 {
   NS_LOG_FUNCTION (this << mrtentry << p << header);
   NS_LOG_LOGIC ("Multicast forwarding logic for node: " << m_node->GetId ());
-  // The output interfaces we could forward this onto are encoded
-  // in the OutputTtl of the Ipv4MulticastRoute
-  for (uint32_t i = 0; i < Ipv4MulticastRoute::MAX_INTERFACES; i++)
+
+  std::map<uint32_t, uint32_t> ttlMap = mrtentry->GetOutputTtlMap();
+  std::map<uint32_t, uint32_t>::iterator mapIter;
+
+  for (mapIter = ttlMap.begin(); mapIter != ttlMap.end(); mapIter++)
     {
-      if (mrtentry->GetOutputTtl (i) < Ipv4MulticastRoute::MAX_TTL)
+      uint32_t interfaceId = mapIter->first;
+      //uint32_t outputTtl = mapIter->second;  // We never use this, do we?
+
+      Ptr<Packet> packet = p->Copy ();
+      Ipv4Header h = header;
+      h.SetTtl (header.GetTtl () - 1);
+      if (h.GetTtl () == 0)
         {
-          Ptr<Packet> packet = p->Copy ();
-          Ipv4Header h = header;
-          h.SetTtl (header.GetTtl () - 1);
-          if (h.GetTtl () == 0)
-            {
-              NS_LOG_WARN ("TTL exceeded.  Drop.");
-              m_dropTrace (header, packet, DROP_TTL_EXPIRED, m_node->GetObject<Ipv4> (), i);
-              return;
-            }
-          NS_LOG_LOGIC ("Forward multicast via interface " << i);
-          Ptr<Ipv4Route> rtentry = Create<Ipv4Route> ();
-          rtentry->SetSource (h.GetSource ());
-          rtentry->SetDestination (h.GetDestination ());
-          rtentry->SetGateway (Ipv4Address::GetAny ());
-          rtentry->SetOutputDevice (GetNetDevice (i));
-          SendRealOut (rtentry, packet, h);
-          continue; 
+          NS_LOG_WARN ("TTL exceeded.  Drop.");
+          m_dropTrace (header, packet, DROP_TTL_EXPIRED, m_node->GetObject<Ipv4> (), interfaceId);
+          return;
         }
+      NS_LOG_LOGIC ("Forward multicast via interface " << interfaceId);
+      Ptr<Ipv4Route> rtentry = Create<Ipv4Route> ();
+      rtentry->SetSource (h.GetSource ());
+      rtentry->SetDestination (h.GetDestination ());
+      rtentry->SetGateway (Ipv4Address::GetAny ());
+      rtentry->SetOutputDevice (GetNetDevice (interfaceId));
+      SendRealOut (rtentry, packet, h);
+      continue;
     }
 }
 
diff --git a/ns-3.10/src/internet-stack/ipv6-l3-protocol.cc b/ns-3.10/src/internet-stack/ipv6-l3-protocol.cc
index 0286b14..76c7a92 100644
--- a/ns-3.10/src/internet-stack/ipv6-l3-protocol.cc
+++ b/ns-3.10/src/internet-stack/ipv6-l3-protocol.cc
@@ -910,31 +910,31 @@ void Ipv6L3Protocol::IpMulticastForward (Ptr<Ipv6MulticastRoute> mrtentry, Ptr<c
   NS_LOG_FUNCTION (this << mrtentry << p << header);
   NS_LOG_LOGIC ("Multicast forwarding logic for node: " << m_node->GetId ());
 
-  // The output interfaces we could forward this onto are encoded
-  // in the OutputTtl of the Ipv6MulticastRoute
-  for (uint32_t i = 0 ; i < Ipv6MulticastRoute::MAX_INTERFACES ; i++)
+  std::map<uint32_t, uint32_t> ttlMap = mrtentry->GetOutputTtlMap();
+  std::map<uint32_t, uint32_t>::iterator mapIter;
+
+  for (mapIter = ttlMap.begin(); mapIter != ttlMap.end(); mapIter++)
     {
-      if (mrtentry->GetOutputTtl (i) < Ipv6MulticastRoute::MAX_TTL)
-        {
-          Ptr<Packet> packet = p->Copy ();
-          Ipv6Header h = header;
-          h.SetHopLimit (header.GetHopLimit () - 1);
-          if (h.GetHopLimit () == 0)
-            {
-              NS_LOG_WARN ("TTL exceeded.  Drop.");
-              m_dropTrace (header, packet, DROP_TTL_EXPIRED, i);
-              return;
-            }
+      uint32_t interfaceId = mapIter->first;
+      //uint32_t outputTtl = mapIter->second;  // We never use this, do we?
 
-          NS_LOG_LOGIC ("Forward multicast via interface " << i);
-          Ptr<Ipv6Route> rtentry = Create<Ipv6Route> ();
-          rtentry->SetSource (h.GetSourceAddress ());
-          rtentry->SetDestination (h.GetDestinationAddress ());
-          rtentry->SetGateway (Ipv6Address::GetAny ());
-          rtentry->SetOutputDevice (GetNetDevice (i));
-          SendRealOut (rtentry, packet, h);
-          continue;
+      Ptr<Packet> packet = p->Copy ();
+      Ipv6Header h = header;
+      h.SetHopLimit (header.GetHopLimit () - 1);
+      if (h.GetHopLimit () == 0)
+        {
+          NS_LOG_WARN ("TTL exceeded.  Drop.");
+          m_dropTrace (header, packet, DROP_TTL_EXPIRED, interfaceId);
+          return;
         }
+      NS_LOG_LOGIC ("Forward multicast via interface " << interfaceId);
+      Ptr<Ipv6Route> rtentry = Create<Ipv6Route> ();
+      rtentry->SetSource (h.GetSourceAddress ());
+      rtentry->SetDestination (h.GetDestinationAddress ());
+      rtentry->SetGateway (Ipv6Address::GetAny ());
+      rtentry->SetOutputDevice (GetNetDevice (interfaceId));
+      SendRealOut (rtentry, packet, h);
+      continue;
     }
 }
 
diff --git a/ns-3.10/src/node/ipv4-route.cc b/ns-3.10/src/node/ipv4-route.cc
index d4134ae..74ed73a 100644
--- a/ns-3.10/src/node/ipv4-route.cc
+++ b/ns-3.10/src/node/ipv4-route.cc
@@ -82,12 +82,7 @@ std::ostream& operator<< (std::ostream& os, Ipv4Route const& route)
 
 Ipv4MulticastRoute::Ipv4MulticastRoute ()
 {
-  uint32_t initial_ttl = MAX_TTL;
-  // Initialize array to MAX_TTL, which means that all interfaces are "off"
-  for (uint32_t i = 0; i < MAX_INTERFACES; i++)
-    {
-      m_ttls.push_back(initial_ttl);
-    }
+  m_ttls.clear();
 }
 
 void 
@@ -129,13 +124,36 @@ Ipv4MulticastRoute::GetParent (void) const
 void 
 Ipv4MulticastRoute::SetOutputTtl (uint32_t oif, uint32_t ttl)
 {
-  m_ttls[oif] = ttl;
+  if (ttl >= MAX_TTL)
+  {
+    // This TTL value effectively disables the interface
+    std::map<uint32_t, uint32_t>::iterator iter;
+    iter = m_ttls.find(oif);
+    if (iter != m_ttls.end())
+    {
+      m_ttls.erase(iter);
+    }
+  }
+  else
+  {
+    m_ttls[oif] = ttl;
+  }
 }
 
 uint32_t
 Ipv4MulticastRoute::GetOutputTtl (uint32_t oif) const
 {
-  return m_ttls[oif];
+  // We keep this interface around for compatibility (for now?)
+  std::map<uint32_t, uint32_t>::const_iterator iter = m_ttls.find(oif);
+  if (iter == m_ttls.end())
+    return((uint32_t)MAX_TTL);
+  return(iter->second);
+}
+
+std::map<uint32_t, uint32_t>
+Ipv4MulticastRoute::GetOutputTtlMap() const
+{
+    return(m_ttls);
 }
 
 }//namespace ns3
diff --git a/ns-3.10/src/node/ipv4-route.h b/ns-3.10/src/node/ipv4-route.h
index db89413..3dfb9cc 100644
--- a/ns-3.10/src/node/ipv4-route.h
+++ b/ns-3.10/src/node/ipv4-route.h
@@ -20,7 +20,7 @@
 #define IPV4_ROUTE_H
 
 #include <list>
-#include <vector>
+#include <map>
 #include <ostream>
 
 #include "ns3/simple-ref-count.h"
@@ -146,6 +146,11 @@ public:
    * \return TTL for this route
    */
   uint32_t GetOutputTtl (uint32_t oif) const;
+
+  /**
+   * \return map of output interface Ids and TTLs for this route
+   */
+  std::map<uint32_t, uint32_t> GetOutputTtlMap() const;
   
   static const uint32_t MAX_INTERFACES = 16;  // Maximum number of multicast interfaces on a router
   static const uint32_t MAX_TTL = 255;  // Maximum time-to-live (TTL)
@@ -154,7 +159,7 @@ private:
   Ipv4Address m_group;      // Group 
   Ipv4Address m_origin;     // Source of packet
   uint32_t m_parent;        // Source interface
-  std::vector<uint32_t> m_ttls;
+  std::map<uint32_t, uint32_t> m_ttls;
 };
 
 }//namespace ns3
diff --git a/ns-3.10/src/node/ipv6-route.cc b/ns-3.10/src/node/ipv6-route.cc
index c4de3fc..414b846 100644
--- a/ns-3.10/src/node/ipv6-route.cc
+++ b/ns-3.10/src/node/ipv6-route.cc
@@ -82,13 +82,7 @@ std::ostream& operator<< (std::ostream& os, Ipv6Route const& route)
 
 Ipv6MulticastRoute::Ipv6MulticastRoute ()
 {
-  uint32_t initial_ttl = MAX_TTL;
-
-  /* Initialize array to MAX_TTL, which means that all interfaces are "off" */
-  for (uint32_t i = 0; i < MAX_INTERFACES; i++)
-    {
-      m_ttls.push_back (initial_ttl);
-    }
+  m_ttls.clear();
 }
 
 Ipv6MulticastRoute::~Ipv6MulticastRoute ()
@@ -127,12 +121,34 @@ uint32_t Ipv6MulticastRoute::GetParent () const
 
 void Ipv6MulticastRoute::SetOutputTtl (uint32_t oif, uint32_t ttl)
 {
-  m_ttls[oif] = ttl;
+  if (ttl >= MAX_TTL)
+    {
+      // This TTL value effectively disables the interface
+      std::map<uint32_t, uint32_t>::iterator iter;
+      iter = m_ttls.find(oif);
+      if (iter != m_ttls.end())
+        {
+          m_ttls.erase(iter);
+        }
+    }
+  else
+    {
+      m_ttls[oif] = ttl;
+    }
 }
 
 uint32_t Ipv6MulticastRoute::GetOutputTtl (uint32_t oif) const
 {
-  return m_ttls[oif];
+  // We keep this interface around for compatibility (for now?)
+  std::map<uint32_t, uint32_t>::const_iterator iter = m_ttls.find(oif);
+  if (iter == m_ttls.end())
+    return((uint32_t)MAX_TTL);
+  return(iter->second);
+}
+
+std::map<uint32_t, uint32_t> Ipv6MulticastRoute::GetOutputTtlMap() const
+{
+    return(m_ttls);
 }
 
 std::ostream& operator<< (std::ostream& os, Ipv6MulticastRoute const& route)
diff --git a/ns-3.10/src/node/ipv6-route.h b/ns-3.10/src/node/ipv6-route.h
index e87e678..68747e2 100644
--- a/ns-3.10/src/node/ipv6-route.h
+++ b/ns-3.10/src/node/ipv6-route.h
@@ -22,7 +22,7 @@
 #define IPV6_ROUTE_H
 
 #include <list>
-#include <vector>
+#include <map>
 #include <ostream>
 
 #include "ns3/simple-ref-count.h"
@@ -202,6 +202,11 @@ public:
    */
   uint32_t GetOutputTtl (uint32_t oif) const;
 
+  /**
+   * \return map of output interface Ids and TTLs for this route
+   */
+  std::map<uint32_t, uint32_t> GetOutputTtlMap() const;
+
 private:
   /**
    * \brief IPv6 group.
@@ -221,7 +226,7 @@ private:
   /**
    * \brief TTLs.
    */
-  std::vector<uint32_t> m_ttls;
+  std::map<uint32_t, uint32_t> m_ttls;
 };
 
 std::ostream& operator<< (std::ostream& os, Ipv6MulticastRoute const& route);