Courtesy of David Hancock, here's a mini-howto on configuring Putty for SSH tunnelling. Let's say you have an account on a Linux box (with an IP address of 192.168.2.100) that you can SSH into. Let's say you want to connect to a Trac instance running on port 8000 on a different box (with IP 192.168.2.200), and you can't get directly to port 8000 on the second IP. You can still use your account on the first box and create an ssh tunnel that will allow you to get to port 8000 on IP #2.
Here's David's howto, almost verbatim:
What we'll do is forward port 9080 on the PC to 8000 on 192.168.2.200 (the host/port for Trac). I'm using Putty version 0.54.
1. Start Putty (so you're looking at the PuTTY Configuration screen.)
2. Enter 192.168.2.100 (the IP of the box you can ssh into) in the Host name / IP address box.
3. Check SSH as the protocol (port number should change to 22.)
4. Enter 'trac-tunnel' as the Saved Sessions name, and click Save.
5. Open the Connection list in the left pane.
6. Open the SSH list in the left pane, Click Tunnels.
7. Check X11 Forwarding (in case you need to run X-based applications.)
8. Back on the right side, at the bottom, enter 9080 for source port (there's nothing special about port 9080, it can be any non-used port on your local machine.)
9. Enter 192.168.2.200:8000 as the Destination, leave Local checked.
10. Click Add.
11. Important, easy to forget: Click Session on the left pane, Click Save.
Now your 'trac-tunnel' session will not only connect you to the .100 box, but when you're logged into the .100, it will mediate a tunnel between your PC's port 9080 and port 8000 on 192.168.2.200.
So, let's try it out:
1. Use Putty to open the 'trac-tunnel' connection, and log in as yourself
2. Point your browser to http://127.0.0.1:9080/ and you'll get right in.
You'd repeat Steps 8-10 to add more local port forwardings. Step 11 is easy to forget, so be warned...