freeswitch/conf/minimal/sip_profiles/external.xml

<profile name="external">
  <gateways>
    <X-PRE-PROCESS cmd="include" data="external/*.xml"/>
  </gateways>

  <settings>
    <param name="auth-calls" value="false"/>

    <param name="debug" value="0"/>

    <param name="dialplan" value="XML"/>
    <param name="context" value="public"/>
    <param name="codec-prefs" value="$${global_codec_prefs}"/>

    <param name="rtp-ip" value="$${local_ip_v4}"/>
    <param name="sip-ip" value="$${local_ip_v4}"/>
    <param name="ext-rtp-ip" value="auto-nat"/>
    <param name="ext-sip-ip" value="auto-nat"/>
    <param name="sip-port" value="$${external_sip_port}"/>
  </settings>
</profile>