SIP and OpenWrt

Hi Forum,

I have an issue with IP-telephony. Situation is as follows:
There is a FritzBox 7490 making the internet-connection and working as my SIP-gateway (registrar). Behind the 7490 there is a Fritzbox 4040 running OpenWrt as my firewall.
In my LAN I have a softphone (PhonerLite). As recommended I opened the ports 5060-5063 UPD for the SIP-traffic. That works fine. But using PhonerLite after some minutes beeing in a phonecall I get disconnectet. Does anyone know this issue, or is there a way to find out what is going wrong (tcpdump or something like that) ?
thanks in advice

SIP and NAT is difficult - and I assume your OpenWrt router does just that towards the the fritzbox. I'd start debugging by placing the softphone directly on the fritzboxes' network - if it works there, you need to apply NAT workarounds to your softphone's configuration.

make sure you don't have a Double NAT

thanks for repay. Yes, within the FB-Network it works fine. So I have to troubleshoot the softphone itself. Thanks for the hint