How to move connection point without affecting clients?

Question

Mikrotik

There is such a task:
There is a MT in one place - public, old (MT1) 100.100.100.100 (10.0.0.1/24)
and MT in another place - new, not registered on clients (MT2) 200.200.200.200 (10.0.1.1/24 )
and host 10.0.1.100 with a moving service from the old address
, it is necessary to forward the connection without reconfiguring clients, and then decide with clients
it is necessary to organize a connection to the host behind MT2, forwarding the connection through public MT1
what has been done:
a GRE tunnel is organized between MT1 and MT2 , OSPF on top of it, routing works
on MT1, the port is exposed outside and using netmap it redirects packets to the internal address from the MT2 subnet
what happens to the packet - it comes to MT1 from the Internet -> netmap to the internal address -> GRE tunnel -> MT2 -> the desired host (it successfully processes it, responds ...)
but! src ip of the packet that received the host = ip of the client, so the packet tries to send MT2, and it must somehow return it to MT1, so that it would already return to the client
which side to approach, where and when the src address should change and how, so that the packet returned along the planned route?
I understand that it seems that I need to mark the connection, and send it back in another way, but I don’t understand how to do it

Answer 1

In theory, source-IP-policy-routing, but I don't know if Mikrotik can do this ...

Answer 2

Mangle to help you, mark incoming packets, then based on them connections and routing through mangles back.