Hi everyone. I need some ideas to solve my issue please:

I have the following scenario: Two buildings of differente enterprises with overlapping lan networks 172.16.254.0/24.
I Need to have communication between these two lan networks, but change the IP range is not an option on both sides. Double NAT, how was explained on that topic: viewtopic.php?t=44154 isn't possible too, cause at the enterprise2 building they have a firewall called STARTI, and that firewall doesn't support that.

(Mikrotik) --> Fiber --> (STARTI)

Any ideas?

Create a management VLAN with different and no overlapping subnets at each building. That will allows communications between the 2 buildings BUT the question is traffic flow between the 2 buildings can only be enabled if there is some sort of NAT for the subnets that are overlapping to avoid the conflict. Some applications might break if they don't support NAT like VoIP.

Check also the option to use separate VRFs but there are some caveats / considerations to explore to make it work.