This is configured at the switch level, the file to look at is /etc/freeswitch/autoload_configs/switch.conf.xml
The parameters rtp-start-port and rtp-end-port are commented out because 16384-32768 are the default values. If you change anything in this file, you will need to restart FreeSWITCH.
thank you and yes I know that, but I must change iptables rules for that
It would be better if there were settings to change the rtp ports that also changed the roles of the iptables
and you say there were not? am I right?