My setups:
- SIP client => OpenWRT => fritzbox (VOIP)
- SIP client => OpenVPN on OpenWRT => fritzbox (VOIP)
Both setups worked fine before I updated the OpenWRT router to the new version 18.0.6.(1).
After update only the first setup is working fine.
If I use VPN no audio goes through. The following packages are already installed:
kmod-nf-nathelper-extra, iptables-mod-conntrack-extra and kmod-ipt-raw
Here seems to be a solution for my issue:
https://forum.openwrt.org/t/sip-phone-problem-to-fritzbox-over-openwrt-18-06/19282/7
but I don't now how I can add a iptables rule with "Helper SIP".
Can somebody help me?