use broadcast func

EduNetworkBuilder/NetworkDevice.cs

@@ -2135,7 +2135,7 @@ namespace EduNetworkBuilder
                     tPacket.OutboundIP = tPacket.destIP;
                     tPacket.TsourceIP = null;
                 }
-                else if(tPacket.destIP.GetIPString != NB.BroadcastIPString)
+                else if(!tPacket.destIP.IsBroadcast())
                 {
                     //it needs to go to a gateway.  Set the next destination is the GW
                     tPacket.OutboundIP = dest;