I 've a very strage problem with open access wireless networks and windows clients.
I'm using a RB2011UiAS-RM and a old wireless controller from 3com (WX1200).
With hotspots set on mikrotik and closed networks (wpa2 tkip) on the wireless controller everything properly works.
On the other hand, with open networks instead of wpa2, windows clients (7, 8 and 10 versions) aren't redirected to captive portal anymore.
Browser shows "Waiting for connection" and after a minute, the connection timed out.
I can exclude a dns problem because with linux, android and apple devices everything works; with windows I can't see the login page also trying to visit the hotspot by its ip.
I tried also to insert in walled garden *.microsoft.com with no results.
I also checked MTU and I can't see any problem with it.
I'm going crazy
Thank you so much!