<p>It seems like this issue is introduced by PCSCF when Soft Phone registers. The SIP Register from PCSCF to ICSCF is as below:</p>
<p>REGISTER sip:ims.mnc001.mcc001.3gppnetwork.org SIP/2.0<br>
Via: SIP/2.0/UDP [FC00:1235:1:0:0:0:0:45];branch=z9hG4bK9fc5.213ad03f122aa3a2b0840eae36a852ba.1<br>
Via: SIP/2.0/UDP [fc00:1235:3:1::]:5060;rport=5060;received=FC00:1235:3:1:0:0:0:0;branch=z9hG4bK2107430722<br>
From: sip:alice@ims.mnc001.mcc001.3gppnetwork.org;tag=60956342<br>
To: sip:alice@ims.mnc001.mcc001.3gppnetwork.org<br>
Call-ID: 2069996946<br>
CSeq: 1 REGISTER<br>
Contact: sip:alice@[fc00:1235:3:1::];line=572ba75522c0a87;alias=[FC00:1235:3:1:0:0:0:0]~5060~1<br>
Max-Forwards: 69<br>
User-Agent: Linphone/3.6.1 (eXosip2/4.1.0)<br>
Expires: 3600<br>
Content-Length: 0<br>
Path: sip:term@pcscf.ims.mnc001.mcc001.3gppnetwork.org:5060;nat=yes;received=**sip:FC00:1235:3:1:0:0:0:0:5060**;lr<br>
Supported: path<br>
Require: path<br>
P-Visited-Network-ID: ims.mnc001.mcc001.3gppnetwork.org</p>
<p>The SIP Register from Soft Phone is fine:</p>
<p>REGISTER sip:ims.mnc001.mcc001.3gppnetwork.org SIP/2.0<br>
Via: SIP/2.0/UDP [fc00:1235:3:1::]:5060;branch=z9hG4bK2107430722<br>
From: sip:alice@ims.mnc001.mcc001.3gppnetwork.org;tag=60956342<br>
To: sip:alice@ims.mnc001.mcc001.3gppnetwork.org<br>
Call-ID: 2069996946<br>
CSeq: 1 REGISTER<br>
Contact: sip:alice@[fc00:1235:3:1::];line=572ba75522c0a87<br>
Max-Forwards: 70<br>
User-Agent: Linphone/3.6.1 (eXosip2/4.1.0)<br>
Expires: 3600<br>
Content-Length: 0</p>

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