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