NAT32 router on windows, firestarter on ubuntulinux.

We have 2 separeted networks in the company, I just wanted to redirect an extern querry from the internet, to a webserver located on the second intranet.
On windows I've been using Nat32.exe as a Router. It's quite easy, just set up all the standard rules, select a network card. Then choose config/application mapping, you have to chose a port and an Ipaddress to forward, if the ports are not standard, you'd better double-click on the application name to change the related script. the syntax is as follows.
exec "ppmap add tcp $port $addr $port"
On a linux machine, you can edit iptable. directly, or use a firewall/router program like firestarter.
Go into policy, allow connections from host, forward service, for example: web on firewall port 8000 to IP adress port 80.
It's not realy difficult. I just had a problem because I was using a hostname, it worked only with the IP address.

ssh secure distant shell

I've not used this yet. It's time I learn how it works. with help from this Ubuntu guide.
to install the server:
sudo apt-get install ssh
then use the client to connect:
ssh user@localhost
enter your password if needed. Et voilà you are connected to localhost, not very interesting. How can you connect remotely from a windows machine?
How do you go arround with the rsa or dsa keys and stuff? see how-to.
On windows you can use the wonderfull program putty to connect to a linux distant ssh server. You can also use winscp, a sort of secure ftp programm.
With putty, you can tunnel the vnc trafic through ssh. using the ssh tunnel on port 5900. Here is a howto. for tightVNC.
I mannaged to connect to a remote linux machine running vncserver. I want to do the oposite: connect from the linux machine to a windows machine running ssh on cygwin. Don't forget to stop the vnc process on linux, so that the port 5900 is free.
The magic formula to create a tunnel:
ssh -L 5900:localhost:5900 windowsuser@host
Then start VNC localhost on linux, there you are :)

ethereal network sniffer

Ethereal is a programm that listens to the network traffic.
There are capture filters for example:
host 192.168.0.1
to see all the traffic comming and going to that host.
Attention, capture filters are different from display filters: an example of a display filter is
http
You'll see only the http traffic --> cool! you can see the user agent, the get requests and the sites visited by a particular host.
After capturing network trafic, you can save the result to a cap file.