If you're having issues with VoIP and this router (revB) Please let us know in detail what you're experiencing.
Who is the carrier?
What ATA are you using behind the DIR-825 revB?
Any type of error message you get from the logs?
When you try to dial out what do you get?
Can you receive or make calls?
Are you able to get to your service provider registration server?
If your service was working before what make, model and firmware was the router?
If you can, would you be able to provide packet captures of LAN and WAN?
I am using the european software version 2.01EU, also see my forum-message http://forums.dlink.com/index.php?topic=7108.0
SIP Registration and callsetup seems to work normally, only the audio-channel setup does not work. The only thing I see when tracing the tcp/ip data is that there is no incoming audio-channel setup.
Also when using DMZ it does not work, while DMZ should pass all traffic without any firewall or portforwarding...
I use several voip providers with SIP protocol, and different clients. One Asterisk server and one Siemens IP-Phone. The same setup works normally with a linksys or other router