The Buffalo firmware is crappy. It doesn't provide any particular NAT functions such as VPN, SIP...etc like the compatitive DLink firmware. The firmware provides most basic functions except the port forward/trigger and the WMM in this model. I have two WHR-G54S, one WHR-HP-G54, and one WZR2-G300N (Nfinite). They can connect Nortel PC client VoIP network phone/conference/video without any problem except this model WHR-G300N. Definitely Buffalo has to make a clear review of this model and fix the firmware with respect to the other Buffalo models.