I am using HT-502 as router behind my cable modem.
I got no problems on voip or normal data transfers but, i am not sure if it is related or not with p2p usage , every 1-2 days, all my port forwarding rules stops working. I got two servers behind this device, (one of them is just using p2p/torrent traffic) with different ports web ssh etc that should be reachable from outside world...Meanwhile Inbound traffic and voip works fine but i can not reach devices behind ht-502 from outside IPs until i reboot the device.
After rebooting it keeps on working 1-2 days more. Then needs another reboot.
I am using HT-502 V1.1C with 220.127.116.11 firmware