freeswitch/conf/autoload_configs/acl.conf.xml

<configuration name="acl.conf" description="Network Lists">
  <network-lists>
    <list name="dl-candidates" default="allow">
      <node type="deny" cidr="10.0.0.0/8"/>
      <node type="deny" cidr="172.16.0.0/12"/>
      <node type="deny" cidr="192.168.0.0/16"/>
    </list>
    <list name="rfc1918" default="deny">
      <node type="allow" cidr="10.0.0.0/8"/>
      <node type="allow" cidr="172.16.0.0/12"/>
      <node type="allow" cidr="192.168.0.0/16"/>
    </list>

    <list name="lan" default="allow">
      <node type="deny" cidr="192.168.42.0/24"/>
      <node type="allow" cidr="192.168.42.42/32"/>
    </list>

    <list name="strict" default="deny">
      <node type="allow" cidr="208.102.123.124/32"/>
    </list>

    <list name="sip_acl" default="deny">
      <node type="allow" cidr="192.168.0.234/32"/>
    </list>

  </network-lists>
</configuration>