Hi,

I have 2 networks (they are about 200 meters from each other).
Both networks have there own internet breakout (gateway)
Both networks have a differeten IP subnet (1 had 172.16.0.0/21 the other has 172.17.0.0/21)
I want to bridge the two netwerks to each oter with 2 SXT-AC devices.

To make it a little more complex.
Between the two buildinges there is a site2 site connection but the speed is not so good.
I like to use the wireless bridge for some traffic (to speed up).
172.16.0/129/27 and 172.17.0.129/27 must communicate over the wireless link of mikrotik (if it is possible.

What configuration must I have?
Can someone help?

They r on the same subnet. Just put your connected SXT on AP Bridge, then scan on the other SXT (to check your loss). And then connect.

They are not no the same subnet.
172.16.0.0/21
172.17.0.0/21

the two SXT-AC should have one interface connect to each subnet (assigne one IP within the subnet) and connect to each other on a different subnet, I'd suggest to use a /30.
then set up routing between the two SXT-AC so they know where to forward traffic for each subnet.

or this can be done by OSPF. many tutorials around for OSPF