Hi,
I can configure kamailio + rtpproxy to enable calling between user behind the NAT. Thanks for the example config, it is very easy to did it.

Do we need rtprpoxy for all kind of NAT?

From what i have read, only symmetric NAT that hard to be traversal-ed. While other type of NAT can be traversaled using STUN.

But my device that behind openwrt router can't work without rtpproxy. Is it expected behaviour?
Or i'm doing something wrong in the config?

Thanks