diff --git a/p4app/controller.py b/p4app/controller.py
index 6f083c4..cd65ce8 100755
--- a/p4app/controller.py
+++ b/p4app/controller.py
@@ -547,8 +547,17 @@ class L2Controller(object):
             tcp_dst_port = pkg[TCP].dport
 
             # FIXME: range, reuse, etc.
-            ipv4_src_addr = self.nat64_session_net[self.mode]
-            self.nat64_session_net[self.mode] += 1
+            idx = self.nat64_session_net[self.mode]['v4_idx']
+            self.nat64_session_net[self.mode]['v4_idx'] += 1
+
+            ipv4_src_addr = self.nat64_session_net[self.mode]['v4_net'][idx]
+            ipv6_dst_addr = ipaddress.IPv6Address(pkg[IPv6].dst)
+            ipv4_dst_addr = int(ipv6_dst_addr) - int(self.nat64_session_net[self.mode]['v6_net'][0])
+
+            log.debug("src v4={}, dst v6 = {}, dst v4 = {}".format(ipv4_src_addr,
+                                                                   ipv6_dst_addr,
+                                                                   ipv4_dst_addr)
+
 
 
             self.controller.table_add("nat64_tcp_session",