For your second question, do not mess with the contact. The proper solution is the path extension. See the path module. — Sent from mobile, with due apologies for brevity and errors. > On Aug 21, 2021, at 6:19 AM, Thomas Grande &lt;tgrande(a)aligera.com.br&gt; wrote: > >  > Hi there! > > I bumped into this post to perform forwarding of REGISTER requests and > then > saving a local cache on 2xx replies from main Registrar: > > https://lists.kamailio.org/pipermail/sr-users/2020-October/110779.html > <https://lists.kamailio.org/pipermail/sr-users/2020-October/110779.html> > > I think I understand all the steps described, but some features I need > are missing: > - How to change the Via headers to perform topology hiding? I > understand TOPOS and TOPOH do not work on these types of messages. > - Change contact header so that registrar responses traverse the > Kamailio box. (Use textops I suppose?) > - Besides, is this approach still the best in comparison to OpenSIPs > mid-registrar module? > > Thanks in advance, > > -- > *Thomás Alimena Del Grande* > Engenharia - Aligera > Tel. 51 3500-0121