[MacTUG] Cisco VPN troubleshooting: how to disable IPv6 with WiFi for Mac OSX

[Keith Peck]

Hi Everyone,
Some Mac OSX users who are fully up to date with the latest version of Mac OSX and the latest version of Cisco AnyConect VPN are still having issues trying to make a VPN connection from their home network.

When attempting to launch Cisco AnyConnect they will see a prompt from stating “/!\ The VPN client was unable to successfully verify the IP forwarding table modifications. A VPN connection will not be established.”

Disabling IPv6 for WiFi has fixed this issue for several people.

Here are the steps to disable IPv6 for WiFi on any MacBook laptop (IPv6 is not used for most of North America so you can leave it turned off for your WiFi on the MacBook unless you are traveling outside the continent.)


  1.  Open "System Preferences", then select "Network" (or click on the WiFi icon on the menu bar near the upper-right of your display, and then select “Open Network Preferences…” from the drop-down list.)
  2.  Click "WiFi" in the list of network services along the left side of the window.
  3.  Click the "Advanced..." button near the lower-right corner of the window.
[cid:image001.png at 01D4DFC8.99734A70]

  1.  On the "TCP/IP" tab (2nd tab from top-left); near the middle of the window for the Configure IPv6 settings, click the drop-down list and change it from "Automatically" to be "Link-local only"
  2.  Click the "OK" button at the bottom-right of the Wi-Fi window which will close the WiFi settings window and return you to the Network  Preferences window.
[cid:image002.png at 01D4DFC8.99734A70]

  1.  Click the "Apply" button at the bottom-right of the Network window.
  2.  Then turn WiFi OFF, wait about 10 seconds, then turn WiFi back ON.
[cid:image003.png at 01D4DFC8.99734A70]

  1.  Make sure you are connected to your home wireless network, and then try connecting to Cisco.
  2.  Close the System Preferences window.

When travelling, especially in Asia’s far-eastern and south-east sections (China, Japan, Korea, Malaysia, Philippines, etc.) IPv6 should be re-enabled by making the change in step #4 back to “Automatically”, then “OK”, “Apply”, and turn Wi-Fi off, and then on.

Keith Peck
Computing Consultant, Client Services,
Information Systems and Technology
University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1.
EC2 2018E, (519) 888-4567 x.47770
kdpeck at uwaterloo.ca<mailto:kdpeck at uwaterloo.ca>


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