DAC settling time and output signal bandwidth
From what I've seen in datasheets, it looks like the ringing will usually be a few octaves above the bandwidth implied by the settling time (1/T).  If that's what's really going on, a low-pass filter should help to dampen that ringing out.  On the other hand, I rather suspect that the actual bandwidth and ringing are influenced more by the impedance of the load the DAC is connected to, and the settling time listed on the datasheet is going to be the optimal case caused only by the parasitic capacitance of the DAC itself.