Take two modules out of range (1 and 2). Put a 3rd module in between the two that is in range of both 1 and 2. Then send data from 1 to 2 via 3. To administrate that the mesh works, power off 3 and let the network fail. Then power on a 4th radio that is also in range of 1 and 2. The connection will be re-established.