How to create a racially correct VPN tunnel?

Question

Mikrotik

I will say right away that I have never been involved in the creation of such an infrastructure, but due to the nature of my activity, I had to face it.
We have office A in one city. There is office B in another city.
In office A on CentOS, set up an OpenVPN server. Office B has a microtik. It raised the connection to Office A using certificates.
Now the task. Opening Office A-1 in the same city, you need to set up a VPN to Office A. What is the best way to implement this? VPN access is provided only to 1c and the telephony server

Answer 1

If there is already an openvpn server in office A, then why bother with something else, install openvpn in office A1

Answer 2

Create a scheme if you want to get a qualified solution here.