How to use one connection to the Internet for VPN and another for accessing other websites?

Question

I have two network cards. If I connect to a network using VPN then to access other websites I have to pass through a proxy server.

Is it possible to use my other network card to connect to the Internet directly without passing through the proxy?

Answer 1

Yes, it can be done, but depending on your current configuration the answer may vary. So I need some extra information:

1. Your operating system
2. The output of the command route -n (if you are on Linux) or route print (if you are on Windows) both before and after you connect to the VPN, and when you are connected to the Internet over your second network card
3. If you are not connected to the VPN, can you use that line to navigate on the Internet?
4. Also, please give the output of ifconfig (Linux) or ipconfig /all (Windows).

Thanks.

Answer 2

What you are asking is called "Split DNS" or "Split Tunneling". The VPN appliance must support this OR you can manually enter the IP address and hostname information into your hosts file.

From How to set up a split-tunnel VPN in Windows Vista:

You also asked about split tunneling, so let's take a moment to explain that concept before walking through the process of creating a VPN connection. By default, when you create a VPN connection, Windows funnels all of the communications from your computer through the VPN. So, if you're logged into a corporate VPN from home to check your email, all of the other Web surfing you're doing on your computer is also being run through your corporate network. This is the default behavior because, from the company's point of view, it's the safest way and ensures all traffic is protected regardless of the destination.

You might not want this behavior, however, for a couple of reasons. First, it allows your company to inspect all of your personal Web traffic while connected to the VPN. Second, it will likely slow down your access to the Web, as everything must first be sent through the VPN.

Split tunneling, on the other hand, configures the VPN connection so that only traffic headed to computers on the corporate network is sent through the VPN connection. Other traffic leaving your computer goes out through your normal network connection.

Follow these steps to set up a VPN connection in Windows Vista that uses split tunneling:

1. From the Control Panel, choose "Network & Internet."
2. Click "View Network Status and Tasks."
3. Click "Manage Network Connections."
4. Right-click on your VPN connection and select "Properties."
5. Select the "Networking" tab.
6. Highlight "Internet Protocol Version 4 (TCP/IP v4)."
7. Click "Properties."
8. Click "Advanced."
9. Uncheck the "Use default gateway on remote network" box.
10. Click "OK" three times to close the windows you opened.

From that point forward, only traffic destined for your corporate network will be sent through the VPN. All other traffic will use the local network.

EDIT1

The information that the Cisco VPN client is used wasn't in the original post, and it basically changes everything and much complicates any final solution.

The biggest problem is that the VPN server must have been configured to allow split tunneling. Otherwise, it just sandbags you in your computer.

Second, you can attempt to configure according to the Cisco article Configuring Cisco VPN Client 3.5 and the Cisco Integrated Client to Secure Nonencrypted Traffic While Using Split Tunneling.

However, I can recommend from my experience one solution that solves the problem without any additional configuration. This solution is simply to install and call the Cisco VPN client from a virtual machine. Even if the Cisco client then attempts to sandbag you in, it will only sandbag the virtual machine, rather than your computer. Your own computer stays free and able to use the Internet, while the VPN is used from the virtual machine.

EDIT2

The Cisco VPN client creates a tunnel, which can be voluntary or compulsory. The type of the tunnel is dictated by the administrator of the VPN server to which you connect. The compulsory tunnel will cut off all access to any external computer, including the LAN, and is what I called the "sandbox".

For more information, see Compulsory Tunneling in the following articles.

• VPN Tunneling - Safe Passage for Data
• Layer 2 Tunneling Protocol (Wikipedia)

If you wish to become an expert in everything VPN, a good book is most recommended, since there is just too much information.