title: Authentication issue during registration with Kamailio server
body: <p>I have a typical requirement, where I have a forwarding SBC between an endpoint and kamailio as shown below.</p>
  
  <p>Endpoint ----> SBC ------> Kamailio</p>
  
  <p>From endpoint I am sending REGISTER request. It reaches SBC. SBC sends the REGISTER request to Kamailio, Kamailio challenges it (401), and challenge response is received at endpoint through SBC.</p>
  
  <p>Next endpoint adds authorization header and sends REGISTER to SBC, SBC forwards it to Kamailio.</p>
  
  <p>Now Kamailio again responds with 401.</p>
  
  <p>When we analysed Kamailio logs, we can see Kamailio log authorization response token and response token that was sent by Endpoint are same.</p>
  
  <p>So my question is, why Kamailio sends 401 repeatedly even if it received proper Authorization header.</p>
  
  <p>Is it because Kamailio received REGISTER from IP address different from endpoint.</p>
  
  <p>Please guide, how can I avoid this issue.</p>