Hi Gdiana,
There are FIFO, LIFO, FILO … rules and there is also a GIGO rule you used in your post…
Please read this: http://forum.mikrotik.com/t/forum-rules/173010/1 and then please redescribe your problem.
What modem? What router? The newtork diagram. The configuration.
The more details, the better answer would be..