[FreeNX-kNX] NX Client stuck at "Negotiating link parameters"

[mathis.schmieder at daimler.com]

Hello everyone,

I am currently experiencing lots of problems setting up a working FreeNX 
configuration. The usecase is connecting from Windows clients to Linux 
workstations running RedHat Enterprise Linux 5. Our Windows and Linux 
networks are heavily firewalled (one reason why we chose FreeNX), but SSH 
connections are allowed. I have no problems whatsoever connecting to the 
Linux network using my own account or the "nx"-account, public key 
authentication works, too. When I try to connect using NoMachine's NX 
Client, I get stuck at "Negotiating link parameters". Looking into the SSH 
log file, every time NX Client reaches the negotiating part I get a 
"channel 2: open failed: administratively prohibited: open failed". I 
tracked this down to some ssh tunneling problems but the only solution I 
found was adding AllowTcpForwarding to the sshd_config, which I did, but 
the problem still exists.
Even trying to connect from one Linux machine to another fails, I get the 
same errors. The only way I could ever get a connection to work was 
connecting locally with encrypt all traffic disabled.
To be honest I am absolutely out of ideas where to search and what to try, 
so if anyone of you got a suggestion - that would be awesome!

Finally some versions:
RedHat Enterprise Linux 5
Freenx-server 0.7.3-11.el5
NXClient 3.3.0

Thanks in advance,
Mathis Schmieder

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