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
Hello, SInce the patch of our ISE platform 2.6 from patch 7 to 8 , SMS sending to guest is not working. Unfortunately, I'm not able to find any logs or reports to troubleshout the issue. I just see the error message from sponsor portal :&nb...
Hello, I'm looking for help in creating an ipsec between a dlink dwr-925 and a cisco ASA. On the dlink I've had to tick the box to set the IKE and IPSEC proposal as it kept sending the wrong DH group no matter what i had configured on the dlink....
Resurrecting previous unanswered question in a more appropriate forum: I need to force anyconnect client due to security reasons as it denies local LAN Access, enables firewall rules, inserts routing table entries, and forces DNS by default, where op...
I am the Network On the left hand side(FW1 and R1), and FW1 Outside int IP is a nat from R1(so I need to enable NAT-T on FW1 for that).I can reach behind the FW3 as long as it does not nat the IP that I am trying to reach, due to the IP limitations to man...
Dear Members, I am new to ASA Firewall. I want to add remote Networks for an existing tunnel, but i have no idea how to go to the config of the existing tunnel from the command line, as there are multiple tunnels configured.. Kaleem