diff --git a/EduNetworkBuilder/NetworkDevice.cs b/EduNetworkBuilder/NetworkDevice.cs
index c8852c3..fe30f6d 100644
--- a/EduNetworkBuilder/NetworkDevice.cs
+++ b/EduNetworkBuilder/NetworkDevice.cs
@@ -3290,7 +3290,12 @@ namespace EduNetworkBuilder
                 //Console.WriteLine("  Tracert bounce: " + tPacket.OrigTTL + " " + hostname + " " + tPacket.payloadData);
 
                 //Finish setting up the new packet - sending it back
-                nPacket.sourceIP = new NB_IPAddress(NB.ZeroIPString);
+                // respond from requested address, not outgoing address: important for routers.
+                if (HasIPAddress(tPacket.destIP))
+                    nPacket.sourceIP = tPacket.destIP;
+                else
+                    nPacket.sourceIP = new NB_IPAddress(NB.ZeroIPString);
+
                 nPacket.TsourceIP = new NB_IPAddress(NB.ZeroIPString);
                 myNet.addPacket(nPacket);
                 //Console.WriteLine("  Tracert bounce pkt:" + nPacket.OrigTTL + nPacket.payloadData);