This instructable is to provide a helping hand to those who are setting up or thinking about setting up a hamachi server. If you are already running a hamachi server you can skip over to Step 4 now. The ultimate challenge a hamachi user can face is to bypass the dreaded Class C error. If you play games, Valve ones anyway, you probably know what I'm talking about. (But for those who don't: It's an error that is confronted when someone on a virtual network tries to join a gaming server that is set as local, but is over the internet because it's running through a virtual network.) I've used hamachi for around 3-4 years now and I've finally managed to master it's ways (it is a very confusing program). With this instructable, you will be taught of the setup, basic principles and not so basic principles of Hamachi as well as how to bypass Class C.

The Basic Concept of Virtual Networking.
The easiest way to grasp the principles of Virtual Networking is to think of a virtual network like a normal network, only it's on the internet not in your house or office building. When you run a Virtual Networking Client such as hamachi and join a virtual network, it's like plugging another Ethernet cable into a hypothetical router. The number of people on a Virtual Network is limited to those who have been given access to it and therefore, you are not vulnerable in using a Virtual Networking Client.

Step 1: Basic Setup - Download the Files.

This is the easy part. Simply download the hamachi setup from LogMeIn! Download it to wherever, you'll be deleting the setup exe after it's installed. It might be a good idea to register as you wait for the download.

What you will need:

A computer.
A reasonable Internet connection. Over 2MB/s at least.
Hamachi (Free Version) : https://secure.logmein.com/products/hamachi/vpn.asp

Step 2: Basic Setup - Installation

Run the installation executable downloaded in the previous step. The setup is quite easy. Make sure you read it instead of just clicking Next at 100 miles per hour.

A few things I'd like to point out:

Check the box saying "Disable vulnerable Windows services over Hamachi", this stops other members of your network from looking at your shared files.
Use the Non-commercial (free for personal use) license unless you: a) Own hamachi. or b) Want to use the trial. It's alright if you use the trial, it just reverts to the free version after it runs out.
Make sure everything installs properly (see last screen below).

Step 3: Basic Setup - Running for the First Time

Run hamachi for the first time. You should be shown a message on what to do to get started as shown below. Follow the instructions shown in the "Hamachi Quick Guide" window. Follow normal net-safety procedure. Use a nickname that isn't your real name. By default, the name will be the name of your computer. When you press the "power-button", Hamachi will go online and you will have an allocated hamachi IP address. Create or join a network by clicking the button with a triangular shape on it. If you want to get a friend to join your network, you will need to tell them the name and password for it so remember not to make it the same password you would use for anything else. The Quick Guide will guide through all the steps needed to get hamachi up and running.

This concludes the Basic Setup section of this instructable. Continue to step 4 for Advance Setup instructions.

Step 4: Advanced Setup - Hamachi Settings

This is where it gets interesting. So far you have a nice, working Virtual Network. It's running very basically and most network-enabled applications will not work, for the same reason you get the Class C error. This step and the following steps will show you how to make your virtual network seem more like a real network to your applications.

The first step in this Advance section is to change the Hamachi settings. Go ahead and click the "System Menu" button in hamachi (the one with the gear on it). Then the Preferences.. button. The status and configuration window should appear.

The main things that should be changed are:
Under the "Window" menu:

Show "Advanced..." peer menu item should be ticked. This is very important!
Double Click Action. I like to change this to Send instant message because: a) Hamachi pinging is rubbish, it doesn't ping an alias even when one is assigned. b) It gives it a messenger feel.

Under the "System" menu:

"Run hamachi as a system service..." this makes hamachi run as a system service. (hamachi will start even if you aren't logged in with this enabled)
"Start hamachi when I log onto Windows" This is handy if you are using a VNC alongside Hamachi (see my other instructable).

Under the "Security" Menu:

"Block vulnerable Microsoft Windows services" This should be ticked unless you want people on your virtual network to see shared files.

Under the "Presence" Menu:

Enable online presence. This isn't necessary but again it gives hamachi a messenger feel. It shows the status of other users.

Step 5: Advanced Settings - Network Priorities (Windows XP)

It's time to get your priorities straight! (in a good way) In this step, we will change the network priority on your computer so hamachi is set to highest. To do this (on Windows XP) go to Start> Control Panel> Network Connections. At the top of the screen (where File, Edit, View, etc. is) you should see an "Advance" menu item. Click on it then click "Advanced Settings...". In the window that appears, select the Hamachi connection in the top box then press the up button to the left of the box until it's highest on the list (making it the highest priority). Click OK and close the "Network Connections" Window.

NOTE: This procedure is different in Windows Vista and Windows 7. I'll probably add a Vista and 7 version of this step later.

Step 6: Advanced - Aliases

This step involves setting aliases for people on your network. An alias is an IP address that is different to a virtual network member's real address in order to make it in the range of your own address. We do this because an IP address for example, 192.164.61.3, wouldn't be on the same network as one like 194.113.0.8 (they are in different ranges). When a computer is connected to a router it is given an IP address that relates to the routers default gateway address, for example: a router's default gateway address may be 192.524.0.1 making the computer's something like 192.524.0.2.

To set up aliases in hamachi, right-click on a network member in hamachi's main window and click "advance..." Set the alias of the "peer" to the same address as yours except for the last digit. You can also change the second last digit but unless you need to, don't (just in case). Also, don't make two peers have the same alias because you won't be able to see one properly if you do. Get your other network members to carry out this step. Now you have made an alias you will have to use command prompt (Start>Run>Cmd>OK) to ping the peer (like I said hamachi doesn't ping aliases, only real IP addresses.). Type "ping [ALIAS IP HERE]" (without inverted commas and brackets) to ping the peer.

Step 7: Finishing Up - Using Your Virtual Network

Use hamachi to run LAN applications over the internet! After completing steps 4-6 you should now be able to run any LAN game you like over the Virtual Network so there is no hassle in trying to find game servers with your friends on them. Following these steps should help you avoid C Class errors.

A few NOTES:

Apparently it is better to have a Vista computer running a game server when you have two different kinds of OSes.
In Valve games start the server as a LAN game then type sv_lan 0 in console, this may help if you are still having connection troubles.

DISCLAIMER: I WILL NOT TAKE ANY RESPONSIBILITY FOR YOUR ACTIONS IF YOU USE HAMACHI OR ANY OTHER INFORMATION INCLUDED IN THIS INSTRUCTABLE FOR ILLEGAL PURPOSES

Please feel free to comment on and rate this instructable. PM me if you find any mistakes.

ENJOY!
EaglesNestOne