[Freeswitch-users] How to enforce freeswitch replying to the source port instead of to the one specified in v/m header parametes (Symmetric NAT)

[Tzury Bar Yochay]

Hi,

I am struggling with a cellular operator which removes the rport from
the SIP messages sent by  the client.
During the troubleshooting process I have been playing with the NDLB
parameters I found mentioned at the fs-wiki

<param name="NDLB-force-rport" value="true"/>
<param name="NDLB-received-in-nat-reg-contact" value="true"/>

as well as with sip-force-contact at the extension xml config file.

<variables>
    <variable name="sip-force-contact" value="NDLB-connectile-dysfunction"/>
</variables>

I Want to make freeswitch replying to the source port instead of the
port supplied by the client, that is
to port 12543 instead of to the 7608 as you can see below some pcap
dumps of the case.

I am not sure if that would solve thep roblem and am open to other
suggestions as well.

Thanks in advance,
Tzury

pcap dumps below:

### REGISTER ###
User Datagram Protocol, Src Port: 12543 (12543), Dst Port: sip (5060)
REGISTER sip:example.net SIP/2.0
v: SIP/2.0/UDP 212.154.128.222:7608;branch=z9hG4bKPj41fa0abd044c35c75598d561b2f93167
Max-Forwards: 70
f: <sip:1013 at example.net>;tag=9194adecbf8e8179530eb589e83631db
t: <sip:1013 at example.net>
i: ebf2e3c254517938f90f33d8fd89326d
CSeq: 17355 REGISTER
m: <sip:1013 at 212.154.128.222:7608>
Expires: 300
l:  0

### 401 UNAUTHORIZED ###
SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP
212.154.128.222:7608;branch=z9hG4bKPj41fa0abd044c35c75598d561b2f93167
From: <sip:1013 at example.net>;tag=9194adecbf8e8179530eb589e83631db
To: <sip:1013 at example.net>;tag=166HraN0B149g
Call-ID: ebf2e3c254517938f90f33d8fd89326d
CSeq: 17355 REGISTER
User-Agent: FreeSWITCH-mod_sofia/1.0.3-exported
Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, PRACK, MESSAGE, SUBSCRIBE,
NOTIFY, REFER, UPDATE, REGISTER, INFO, PUBLISH
Supported: timer, precondition, path, replaces
WWW-Authenticate: Digest realm="example.net",
nonce="f2f1370c-bc7c-11de-b000-fbe81e221ab4", algorithm=MD5,
qop="auth"
Content-Length: 0