It is all about how you want things to run, FS allow to have multiple profile each of them can work on different ip considering that all users can call each other even they are registered on different IPs

here is below and example:

profile1:
     Name—> Internal
     IP      —> 192.168.1.1
     SIP Port —> 5060
 Sip_profile.xml:    <param name="ext-rtp-ip" value=“192.168.1.1"/>
  <param name="ext-sip-ip" value="192.168.1.1”/>


Profile2:
    Name —> internal_nat
    IP       —> 192.168.1.1
    SIP Port —> 5065  —>(Port Forwarded on Router to —> RealIP:5060)
Sip_profile.xml  <param name="ext-rtp-ip" value="auto-nat"/>
  <param name="ext-sip-ip" value="auto-nat"/>

However of the above configuration still both internal and external will be able to call each other based on the below dial string , the “*/“ assure that users from different profile can call each other 

   conf/directory/default.xml :   <param name="dial-string" value="{^^:sip_invite_domain=${dialed_domain}:presence_id=${dialed_user}@${dialed_domain}}${sofia_contact(*/${dialed_user}@${dialed_domain})}"/>



On Feb 18, 2016, at 12:17 AM, freeswitch-users-request@lists.freeswitch.org wrote:

From: Dan Edwards <DEdwards@vertical.com>
Subject: [Freeswitch-users] Can FS offer both internal & external IP address?
Date: February 18, 2016 at 12:16:47 AM GMT+3
Reply-To: FreeSWITCH Users Help <freeswitch-users@lists.freeswitch.org>


I'm running FS behind Nginx, so I explicitly removed the local IP address from localnet.auto. This forces FS to always offer 'ext-rtp-ip'. Outside users work fine in that scenario.

Internal users also work, as long as we turn on NAT reflection in our router. I'm looking for a way to not require that router change.

If I can get FS to offer up both it's internal IP and 'ext-rtp-ip' as candidates in the initial INVITE, the browser could then use ICE to determine which IP address was correct. 

Is there a way to offer both and allow ICE on the client side to figure out which one to use?

Thanks,
Dan