freeswitch/conf/minimal/sip_profiles/internal.xml

<profile name="internal">
  <settings>
    <param name="auth-calls" value="true"/>
    <param name="apply-nat-acl" value="nat.auto"/>

    <param name="debug" value="0"/>
    <param name="sip-trace" value="yes"/>

    <param name="dialplan" value="XML"/>
    <param name="context" value="default"/>
    <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="$${internal_sip_port}"/>
  </settings>
</profile>