I tried all the ports. Normally, I connect the monitor using Thunderbolt/DisplayPort mini connector which is on the laptop and it works well with full resolution. The problem is that this way, I can connect only one monitor and have to plug/unplug the cable too often which is inconvenient and I'm afraid about the port (two cables already broke, if the port on the laptop breaks as well, I'm in trouble).
So I would like to use docking stations ports (there are 2 displayports). I don't remember if I patched the framebuffer (maybe, some time ago, I tried everything), but should this be necessary when the monitor works normally using the laptop port?