The error "Error 51: Unable to communicate with the VPN subsystem" is caused by an issue with the interprocess/driver communication.
This document will attempt to track known reasons and workaround/fixes for this error.
Issue 1: PPP network interfaces (unlikely to be seen today)
There is a known issue with Mac OS X 10.4 and the earlier versions of 4.9, such as 4.9.000.0050 when using PPP based interfaces (e.g. Dial-Up). This issue is documented in Cisco bug ID CSCsd51157. A workaround when hitting this issue was to restart the Cisco IPSec VPN Services after the VPN Point-to-Point Protocol (PPP) based connection is up.
Upgrade to Mac OS X 10.4.9 or later and Cisco IPSec VPN 4.9.01.0800 or later.
Issue 2: 64bit Mac OSX Kernel
If one tries to use the Cisco IPSec VPN Client on Mac OS X running the 64-bit kernel one will receive the error 51 failure.
The Cisco IPSec cliet for Mac OS X does not support the 64 bit kernel. The VPN driver only has i386 and PPC extensions, not x86_64 extensions.
To do a test 32bit boot one can hold the 3 and 2 buttons during Apple System Boot. If this works then we have proved that your issue is the 64bit kernel.
1. If running Mac OS 10.6 or later, Use the built-in Mac OS X IPSec client.
2. If the built-in Mac OS X client is unavailable, re-configure your Mac to boot into the 32bit kernel. This issue had not been much of a concern until recently, March 2011, when Apple began to release their Macbook Pro systems configured to boot into 64bit by default
Dear all, Could you please advise me client isolation examples in catalyst switch?Can I achieve it with vlan access map for example first 50 IPs are servers and rest are client machines?Maybe better ways? Please advise me some examples.&nb...
Hello, I struggle to find the right team to answer questions on a renewal for CES. Our partner initially purchased CES that included SMA. When renewing the CES the SMA is not included and further is not a possible choice in CCW for CES.&nb...
Hello Team,We have , Dual SSID BYOD set up – “XYZ-OPEN” open SSID for onboarding, and “ABC-Employee-Register” for BYOD Registered devices- Internal ISE CA for SCEP / BYOD Client Certificates- Certs issued with MAC-in-SAN, and users advised to disable...
Team,We have been doing a PoC on the Cisco ISE as a NAC. Our use case was identifying if the laptop is a corporate owned laptop and if yes allow it the default full access VLAN. If not, give it guest VLAN with limited access. This has been achie...
Before I get into the question, I understand that the better method would be to use a firewall for what I am trying to accomplish however I need to work within the scope of what I have right now, so no new hardware etc. Also the powers that be have ...