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Error 51: Unable to communicate with the VPN subsystem

I upgraded Mac OS X to 10.5.8. I did the upgrade after my hard drive died and imported my profile from an old backup. When I tried to run my Cisco VPN client that I use for work, I was given this error:

Error 51: Unable to communicate with the VPN subsystem

First, I read that I could do this in the terminal:

$ sudo /System/Library/StartupItems/CiscoVPN/CiscoVPN restart

Since I don’t have a CiscoVPN directory under startup items, that didn’t help me. Then I read that you need to to repair disk permissions using disk utility. I did that and it found several inconsistencies. Good stuff, though, it also did not solve my problem.

Then, I read that I could do this:

$ sudo SystemStarter restart CiscoVPN

The command didn’t produce any output, nor did it fix my problem.

Finally, I came across a site that told me to do this:

$ sudo kextunload /System/Library/Extensions/CiscoVPN.kext
$ sudo kextload /System/Library/Extensions/CiscoVPN.kext

This finally fixed my problem. Here is the sequence of commands that I ran and the output:

$ sudo kextunload /System/Library/Extensions/CiscoVPN.kext
kextunload: unload kext /System/Library/Extensions/CiscoVPN.kext failed
$ sudo kextload /System/Library/Extensions/CiscoVPN.kext
kextload: /System/Library/Extensions/CiscoVPN.kext loaded successfully
$ sudo kextunload /System/Library/Extensions/CiscoVPN.kext
kextunload: unload kext /System/Library/Extensions/CiscoVPN.kext succeeded
$ sudo kextload /System/Library/Extensions/CiscoVPN.kext
kextload: /System/Library/Extensions/CiscoVPN.kext loaded successfully

Hopefully, this will save someone some time.

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This entry was posted on Tuesday, October 6th, 2009 at 8:31 pm and is filed under General Agile. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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

  1. Rob Raymond Says:
    October 19th, 2009 at 8:05 pm

    Thank you so much for posting this, it worked like a charm!

  2. Kris Kemper Says:
    October 19th, 2009 at 9:07 pm

    Glad I could help.

  3. David Greenberg Says:
    January 22nd, 2010 at 10:51 am

    Thanks, Kris. I tried a lot of other Terminal stuff, but only your fix worked for me.

    David

  4. Kris Kemper Says:
    April 25th, 2010 at 8:26 pm

    I’ve found this to be a somewhat short term fix. From time to time, the problem comes back and I have to do the steps again.

  5. voice vpn Says:
    August 27th, 2010 at 9:01 am

    If you’re using Cisco VPN client, then VPN error 412 is usually transport settings, although it can be other things. Try clearing the cached password (if it is VPN Client) first. If that doesn’t help, then change the transport settings from UDP to TCP or vice versa. Make sure that your VPN connection is set up correctly with the server and such.

  6. B Campbell Says:
    September 3rd, 2010 at 8:38 am

    This is what worked for me when I had this error:
    http://forum.maas360.com/go/mobileitexpertise/fix-for-cisco-vpn-error-51-unable-to-communicate-with-the-vpn-subsystem/

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