Duke has rolled out specific security requirements for access to the DHE networks. If you use VPN on a personal machine and need to connect to DHE servers ( ie: munin, cluster, etc ) then you are expected to meet specific requirements.

1) Device registered with NAC : NAC Registration 2) Have the NAC agent installed on your local computer 3) Have an approved anti-virus software 4) Have an approved operating system version

You can read more about NAC here : https://nac.dhts.duke.edu/network-access-control-nac