Hello;
    
When I was testing on NatHelper , i  realized that Some Kind of Softphones can use "received" param on Contact for re-register request.
    When re-registartion ,it uses received parameter IP on Contact so that Kamailio cannot understand that it is Natted.
    Kamailio dont send Options request to keep open ports because of not natted. So after a little time , Modem or Firewall close opened ports and  then UAC is unreachable!
    When i have a look ietf3261 , i couldnt find any thing this flow. Do you have any idea about it?
    
I am looking forward to your suggestions.
    
Thanks.
    
    
    First Flow.
    -----------
    UAC sends  Registration --->>
    
    Contact : <sip:123456789@192.168.0.223:5060>
    
    
    Kamailio answer for register <<---200 OK
    
    Contact : <sip:123456789@192.168.0.223:5060>;received=195.8.8.10
    
    Second Flow
    ------------
    UAC sends re-registartion --->> (Oh God there is a received I must send registarion again!!)
    
    Contact : <sip:123456789@195.8.8.10:5060>
    
    Kamailio answer for register <<---200 OK (OK Bro! you aren't Natted. No problem. I dont send Options)
    
    Contact : <sip:123456789@195.8.8.10:5060>
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