Hi.
I have a Mikrotik RouterBoard in my local network. All I need is that every request to a specific subdomain (let’s say sub.example.com) redirects to a local IP (for example 192.168.1.24) without any change in other requests.
I’d appreciate any response. 
What DNSs are set up on the other devices?
Other devices haven't any DNS, our DNS server is the Mikrotik. However, maybe someone sets another DNS on his/her device.
Thank you for your response.
Generally you need a proper reverse proxy (e.g. HAproxy, apache, etc.) to redirect requests per FQDN, ROS can not do it properly.
Thank you. Yes, there are many problems with redirecting with Mikrotik. I changed the plan to use another way.
The only problem “with directing with Mikrotik” is that Mikrotik is a router and firewall and has thus very limited capabilities beyond L4 (i.e. handling UDP/TCP packets). And “redirecting a subdomain” is an L7 (because it has to interact with actual protocol, e.g. HTTPS), which is beyond the scope of Mikrotik.
Which means that the problem is rather with (too high) expectations of MT owner/admin.
Oops! I’m not a network admin, and obviously I don’t have the knowledge. I was trying to do a thing to help my own program work well but due to lack of knowledge or a pro person in the company, I failed and changed the way I’m doing a thing.
Anyway, thank you for your response.
What? You mean that whole OSI 7 layers thing actually means something? 
Amazing how many people don’t understand that…