Hi Folks,

As I promised, now that I have found the issue, I am posting the solution - and it's 
something that I think should be disseminated because it's a fairly common situation 
and I don't think the answer is "out there" (on the web).

The situation is that we are using SSH through a firewall that does network address 
translation, and we are trying to tunnel VNC through that SSH connection. The machine 
behind the firewall cannot "see" the external IP address of the firewall. 

The tunnelling fails if the firewall IP address is used, but it works if the hostname 
is used.

So think about this - If I consider 3 machine and call them client, firewall and 
server, then client needs a hosts file to translate the hostname "server" into the IP 
address of "firewall". When it sets up the tunnel IT TAKES THE HOSTNAME WITH IT TO 
"client". If this is the IP address, "client" doesn't know where to send the return 
packets. If however the tunnel is set up using the hostname, and that hostname 
translates to different IP addresses at either end of the tunnel (i.e. it translates 
to "firewall" for the client, but it translates to "server" for the server) then it 
works.

I could probably find a way of explaining this a bit more clearly, so if this is 
confusing feel free to ask for clarification. It should probably become a mini-howto 
but I doubt that I'll find the time!

Cheers

Ron

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