Hi, Unfortunately, "integration" means many things to many people, and Kamailio is a fairly low-level toolkit, so there is no one-size-fits-all "step-by-step" guide. What you're asking for basically lies in the province of "learning to use Kamailio". If you're looking for turn-key solutions, you may consider hiring a consultant from the Business Directory on the web site[1] to assist. Having said that, based on your message, it sounds like what you need is to use Kamailio to proxy the registration requests upstream to Asterisk. The most straightforward way to do this is to simply t_relay() / forward() the requests, adding a Path header to the REGISTER message along the way[2]. The `path`[3] module can help with the construction. It is not clear whether you want to have Kamailio provide the ITSP interface for the Asterisk PBXs, or whether you want them to call out to the ITSP directly. If the first case, you'll need some way to decide, "This call is coming from the IP address of a PBX I trust". The `permissions`[4] module provides some ready-made concepts for this requirement. Hope that helps. I think you will find this list is very amenable to specific questions about how to do X or Y, but not to "please teach me how to do everything from start to finish". The scope of that request is just much too ambitious. -- Alex [1] https://www.kamailio.org/w/business-directory/ [2] https://tools.ietf.org/html/rfc3327 [3] https://kamailio.org/docs/modules/stable/modules/path.html [4] https://kamailio.org/docs/modules/stable/modules/permissions.html On 10/25/20 10:14 PM, Lorem Ipsum wrote: -- Alex Balashov | Principal | Evariste Systems LLC Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free) Web: http://www.evaristesys.com/, http://www.csrpswitch.com/