I give up! After weeks of pondering and testing we are at out wits end so I turn to you kind sages of the forum for help.
Here's our situation: We have a bunch of stores, and each store has a Mikrotik router managing the network, which is divided into Trusted and Untrusted networks, fairly standard. Every machine my departement sends out (I am in IT) we put TightVNC on so that we can access it fairly quickly should the need arise. TightVNC is especially crucial with the computers we use with advertisement screens, as store employees aren't trained to fix those issues.
Everything was fine two months ago, but as Mikrotik has started updating itself to 6.47, 6.49 and so on we've noticed that we can no longer access any of the untrusted computers on the network managed by Mikrotik.
Our method was simple: we use PuTTY to set up a tunnel to the computer we want to control via Mikrotik's IP, and mirror the VNC port on the target computer to a port on our own. By doing this we are able to connect to the remote computer via localhost:5900. I have attached a dummy example image of our tunnel setup.
This worked for the first month I worked here, but since late August things have started falling apart. We're blocked out of almost every untrusted computer running a mikrotik version greater than 6.44. Most 6.44 connections I tested while writing this works fine. Beyond that, the most common error is this, which appears when you try to VNC to localhost:5900:
PuTTY Fatal Error
Recieved SSH2_MSG_REQUEST_FAILURE with no outstanding global request.
Followed by the connection closing and putty going inactive. I've seen this error dozens of times across different stores and despite my best efforts I've never been able to figure out what exactly goes wrong. It seems to be an obscure bug.
What do I need to do to figure out this mystery? We need to get access to the computers we are currently locked out of. The only thing the problem-mikrotiks have in common is that they've been updated beyond 6.44. The lowest version I could find above 6.44 is 6.47.10. Was there any update that affected SSH connections in updates starting at 6.45?
I could also use a way to export all the settings from a mikrotik into a document so I can easily compare the working vs the nonworking ones and find the thing we need to change. Does microtik have that ability?
I'm thankful for all and any answers. I am leaving the office now so I won't be able to read any answers until tomorrow.
Best,
Helplessnoob