Freeswitch Port Range

Default RTP ports are 10000-50000.

If you want to change RTP ports, you should edit /usr/local/freeswitch/conf/autoload_configs/switch.conf.xml file (find these lines in file):

<param name="rtp-start-port" value="10000"/>
<param name="rtp-end-port" value="50000"/>

And change 'value' to desired ports. For example, if your you want to allow RTP ports 10000-20000, these lines should look like this:

<param name="rtp-start-port" value="10000"/>
<param name="rtp-end-port" value="20000"/>

Forward RTP ports (10000-20000) on your firewall to this Freeswitch machine.

Restart Freeswitch:

service freeswitch restart