See devices between NetoToNet client sites

Good morning,
I have a situation like the one shown in the drawing.
In practice I have a master office and three secondary offices connected to each other in NetToNet with OpenVPN (Blue Arrows).

From the client sites “sees” the devices of the Master site, my question is:

How can I make client sites see devices from other client sites?
Let me explain, how can I see the devices of “Site B” and “Site C” from “Site A”
passing through the existing NetToNet, without having to create NetToNets for example between “site A” and “Site B” (Red Arrows)?

I managed to ensure that a client connected with OpenVPN RoadWarrior by connecting to the Master site also “sees” the devices of “Site A”,
I think the concept is quite similar, but I don’t have much experience, in fact I’m simulating what I want to do.

Thank you
Giuseppe

:thinking: Maybe, on the following page you will find a hint.

Regards

For now, thanks.
I look at it

Giuseppe

I read it, but it’s not what I need.
I have to pass the packets between two NetToNets so that two slave sites see each other.
I work on it but I don’t have much background.

Giuseppe

Have you read the following page?

Sorry for the late reply, but I’ve been quite busy.
I had seen the document, I used it to be able to see my office by connecting via VPN to my home, I have to understand, but first of all study, whether it is also suitable for my request.

Thanks
Giuseppe