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As of August 17th, please download Tunnelblick version 3.8.8b from Do not download 3.8.8c or 3.8.8d and do not update to these versions if the software if offered.

After installing tunnelblick, download the config file. The configuration file is compressed, so double-click it to expand it: you should then get a file 'chemistry.tblk'. ('chemistry.tblk' will not run from the Downloads folder. Copy to the Desktop). Double-click 'chemistry.tblk' to install the configuration.


Select 'Connect Chemistry' from the TunnelBlick icon. The credentials you should use are your ChemNet credentials. These can be collected from and it is OK to tell Tunnelblick to save them. If you are using Chrome as your web browser please type the credentials in, do not cut and paste as this has been proved not to work. Please note that the ChemNet username is your CRSID followed by , not . (There is an option for a Security Code, please ignore, we don't use that.)

Dealing with the warning: 'apparent public IP address was not different after connecting'

This warning appears when connecting using newer versions of Tunnelblick with our latest configuration files. It is a warning, not an error. It happens because in Chemistry and SPRI we configure the VPN to only send network traffic destined for the University of Cambridge over the VPN link, and all other traffic goes direct to its destination. This setup gives the best network performance for videoconferencing, while still allowing you to access University-only resources. There are two ways to avoid the warning:

  • Disable the IP address checking feature using the checkbox on the "Preferences" panel of Tunnelblick's "VPN Details" window.
  • Switch to using a 'Full Tunnel' configuration file. This will send all your network traffic via Chemistry's network when the VPN is on and may be slower. Full tunnel configuration can be downloaded from

System status 

System monitoring page

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