VPN (Virtual Private Network)

Please see secure network warnings before using VPN.

Why use VPN?

By using VPN, you can establish a direct connection to the local network of the Nevis particle-physics systems from the outside. You also get the benefits of the web proxy, in that all your network connections go through our firewall.

Normally, to access a machine on the local network, you use ssh to login to one of the workgroup servers, then ssh again to the local machine. But there are times when this becomes inconvenient, complicated, or slow; e.g., accessing one of the electronics-design systems at Nevis. A VPN connection can be a simpler solution.

If all you want to do is browse the web securely, you may want to consider a web proxy instead. They're a bit harder to set up than VPN, but you don't have to install a program to use it.


VPN works for connections from outside the Nevis particle-physics networks. It does not work when connecting from within that network.

In particular, the Nevis mansion house and wireless connections within the research and electronics buildings are within the network that VPN protects. You cannot use Nevis particle-physics VPN to connect to systems in the research and electronics buildings when you are within the Nevis particle-physics network.

Install Cisco's VPN Client

This only has to be done once.

Although there are many VPN client programs available, since we have a Cisco firewall I find that the Cisco secure client works best and takes advantage of all the networking features.

To get Cisco's VPN client, scroll to the bottom of this page and click on the appropriate link.

If you already have a version of Cisco's VPN software that works, you don't have install another one. Just edit the pop-up menu's VPN servers (just click on the menu and type) to add vpn.nevis.columbia.edu and continue as described below.

Using the VPN client

Start the Cisco VPN client program. You may have to "hunt" for its location. For example, on my Macintosh, I found it in Applications->Cisco.

When you start the application:

  • The VPN server is vpn.nevis.columbia.edu
  • Click on the Connect button.
  • If you're prompted for a Group, choose Nevis
  • Use your Nevis account name and password.

If you have any active network connections (e.g., you have an ssh session open) they'll probably be cut off when you connect to VPN. Just restart the connection to have its traffic go through the secure network.

If you're having trouble accessing your local network devices (e.g., a printer in your home), go into the Cisco client preferences and make sure Allow local (LAN) access is checked. Then disconnect and reconnect VPN.

That's it!

Things to try

Our firewall normally filters out ping attempts to any device inside the Nevis particle-physics networks. Before you start VPN, try to ping mail.nevis.columbia.edu; it will not succeed. After you connect with Cisco's client, ping mail will work.

From outside of Nevis, systems on the local network are "invisible." Once you establish a VPN connection, you should be able to directly ssh to any system on that network; e.g., ssh ekumen.nevis.columbia.edu.

Some systems have restricted access to the outside world, e.g., the electronics-design machines. With a VPN connection, you should be able to directly ping and ssh to a restricted system like elecsim4 (assuming you have an account on elecsim4, of course!).


If you're using Mac OS 14 (Sonoma), try the Ventura client.

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Topic revision: r14 - 2023-10-18 - WilliamSeligman
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