Answered By: Susan Mikkelsen
Last Updated: Sep 09, 2015     Views: 80

Are you getting this error message?

“Error 51: Unable to communicate with the VPN subsystem” 

Follow these steps:

  • Quit the VPN Client
  • Open a Terminal window, (Applications > Utilities > Terminal)
  • Type in - sudo/System/Library/StartupItems/CiscoVPN/CiscoVPN restart
  • Enter your password


Why does this work?

This will stop and start the “VPN Subsystem”, or in other words restart the CiscoVPN.kext extension. Cisco seems to have problems when network adapters disappear and reappear, something that happens commonly in Wireless or Dial-up scenerios. Sometimes putting a system to sleep, disconnecting an Ethernet cable or simply reconnecting your wireless will cause CiscoVPN to loose track of the network adapters on the system. The above hack should side-step all of these issues by causing the CiscoVPN to re-initialize.

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