[OPEN VPN] unique certificate for each secret or caller id

hello
i have a openvpn server work perfect , and i want to specify one and only one certificate for each secret,
c1 =>u1
c2 =>u2


c1=>u2 (should not work)

how i can do it?

As far as I know, you can’t.

I am guessing you want something like this:
https://serverfault.com/questions/358855/how-to-prevent-users-from-sharing-certificates-in-openvpn

Sadly there is no way to config something like that on the RouterOS OpenVPN server. The OpenVPN server in RouterOS is very limited.