How to organize subnet routing in Mikotik?

Question

network hardware

Two different white ips (X and Y) are configured on the router, they are bred to different local subnets (A and B) using packet labeling rules - initially it was necessary to strictly isolate the locales.
Now it is required to provide communication between two specific machines on subnets A and B, and so that they continue to go to the Internet through IP addresses X and Y (I assume that after setting up routes they will have aliases in order to ping each other)
How to do this means of RouterOS?

Answer 1

if Mikrotik is the default gateway in both networks, then it’s enough just not to prohibit such traffic and make the routes available to the PCs of both networks (this is based on the fact that you have routing tables or VRF, this is not required by default).