Thank you for your answers.

I have a old SBC with opensips and it always adds received to Via. However, in my Kamailio it only adds in NAT scenarios. I would like to understand why that happens.

A segunda, 28/09/2020, 17:35, Duarte Rocha <duarterocha91@gmail.com> escreveu:

Greetings,

When NAT is detected in my Kamailio, the proxy add the parameter "received" to the Via header which includes the source IP.

What is the mechanic or function responsible for this behaviour? Does it come from the NATHELPER module?

Best Regards,