How to change rtp address

hello,

please how to change my rtp address without nat ?

What do you mean by “change my rtp address without nat”? Which channel driver are you using (chan_sip or chan_pjsip)? What are you trying to achieve?

On chan SIP you can use the media_address = 172.16.42.1

The IP address used for media (audio, video, and text) in the SDP can also be overridden by using the media_address configuration option. This is only applicable to the general section and can not be set per-user or per-peer.
;

psip also have the above option and external_media_address, read the sample files for each file

channel driver is chan_dahdi

The chan_dahdi module doesn’t use RTP.

in /etc/asterisk i don’t find chan_sip.conf file. i have only chan_dahdi and chan_dahdi_additional files