[SR-Users] Received parameter on Via

George Diamantopoulos georgediam at gmail.com
Tue Sep 29 02:48:31 CEST 2020

Received parameter is always added to via, and is part of the core sip RFC.
This is how responses are routed.

To get nat traversal on kamailio, you generally need the following in

- Received only handles address masquerading, for port translation you also
need to look at rport.
- A way to perform nat traversal for subsequent in dialog requests, and
additionally for initial requests involving location lookup. This is where
nathelper or similar must be involved.
- Prevent UDP Connection Tracking Timeout on NAT boxes (keeping nat alive).
This can be achieved in many ways, including configuration on NATed devices
(low registration expiration, keepalives) but it's better to employ
keepalive functionality by kamailio modules (nathelper or usrloc ka, for

The actual way to perform these tasks is a bit more involved, and I'd
suggest looking at the kamailio sample configuration file which should work
for most cases.

On Mon, 28 Sep 2020, 19:36 Duarte Rocha, <duarterocha91 at gmail.com> wrote:

> 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,
> _______________________________________________
> Kamailio (SER) - Users Mailing List
> sr-users at lists.kamailio.org
> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
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