Mikrotik have the option to define navigation ip ..
Please if you can give me an instructive

If u want to set IP address when your mikrotik is doing src-nat u need to use a src-nat rule and not a masquerade one.

Use something like this:

/ip firewall nat chain=srcnat out-interface=<out ineterface> src-address=<your local net> action=src-nat to-address=<ip on out interface>

You must have IP address configured at out interface.


Is it what you need? if not please send more information.

Jorge