OK, now we're getting into the nitty-gritty. This is proving far more difficult than 
it should be! I've turned on extensive logging of ssh packets and include the relevant 
logs here. First though, let me try to explain the two scenarios - the working and the 
non-working:

I have a PAT on our firewall that redirects SSH traffic to my Linux machine at work. 
So that might look something like this:

 _____                 ______               _______
|     |  SH2 Traffic  |      |             | Work  |
| Home|---------------| PAT  |-------------| Linux |
|_____|               |______|             |_______|
192.168.1.2         172.15.20.1          172.168.10.54
tgl8b/laptop          middleman                cfd1

(I've just made up the IP addresses for the purposes of this example - the PAT is of 
course a non-private IP address).

tgl8b is a linux machine running OpenSSH and linux vncviewer, while laptop is a 
Windows2000 machine running Putty and a windows vncviewer.

So I sit on tgl8b, open an SSH connection to middleman, and that is redirected to 
cfd1. I invoke it with the command

ssh -L5901:middleman:5901

and if I then start vncviewer on tgl8b, everything is fine. If I use laptop, I use 
Putty to connect. I set up the tunnel so that the tunnel window says:
L5901  172.15.20.1:5901
I then start vncviewer, point it to localhost:1 and it *does* connect, but ought to 
then pop up a dialog box asking for a password. It does nothing.

However, if I carry the laptop into work and simply replace the IP address for 
middleman with the IP address for cfd1, and connect as follows:
 _____                             _______
|     |  SH2 Traffic              | Work  |
|     |---------------------------| Linux |
|_____|                           |_______|
192.168.1.2                     172.168.10.54
tgl8b/laptop                         cfd1

Then when I connect to localhost:1 I get a window requesting a password. Once I've 
logged in, up comes the vncviewer and everything is fine.

Now I collected the SSH traffic in a Putty log file from these two cases, and the ONLY 
difference in the log files (apart from the actual vncviewer traffic which isn't 
present in the one that never asked for a password) seems to be that the connection 
through middleman contains a large number of lines saying:

Outgoing packet type 2 / 0x02 (SSH2_MSG_IGNORE)

Any experts out there who would like to see the whole logs, please let me know. If I 
had to guess, I would say that Putty isn't tunnelling the port, it's just forwarding 
it - but that couldn't be the case could it??

Ron







Cheers

Ron

Ron Cresswell
Principal Scientist
James Hardie Research
Ph  +61-2-8845-3382
Fax +61-2-8845-3222
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