I have been using Xnet's Open VFX for over a year now using a Fritzbox Fon WLAN. Last week I added a second VIOP line (to replace a normal Telecom line). Now when one line is in use, I can't call out or receive calls on the second line. The second line does ring but when answered does not connect. Does anyone know how to fix this? The Xnet Support suggested I may need to open another port? But I am not sure how or were to do this.
After hours of trying all sorts of setting I found the problem. There is a setting in the Fritzbox were you enter the available bandwidth. If this is set to low, Fritzbox will limit the number of simultaneous calls so the quality of the calls are not compromised.