Describe what happens starting at time t = 0 ?

One side of glass cylinder is initially filled with H2 at pressure P and other side with N2 at pressure 2P . This glass cylinder is closed at both ends and a glass filter in middle of cylinder divides into two compartments of equal volume . Describe what happens starting at time t = 0 at constant temperature and assuming that pores of filter have a diameter much smaller than mean free path of gases please help ??