Example of opensips SBC with 2 interfaces with full RTP proxy and g729 transcoding. Software: opensips 3.1, rtpengine, bcg729. example settings for rtpengine: OPTIONS=»-i external/172.18.254.50!EXTERNAL_IP -i internal/172.25.150.242 -n 127.0.0.1:2223 -m 35000 -M 65000 -L 4 —log-facility=local1 —table=0 —delete-delay=0 —timeout=60 —silent-timeout=600 —final-timeout=7200 –offer-timeout=60 —num-threads=4 —tos=184 –no-fallback» example opensips config: git clone https://bitbucket.org/yooxy/opensips-sbc-local-external-transcode.git