Prior to upgrading to Lion there were no issues using Cisco's VPN Client (4.9.01). With Lion, Error 51 is being returned stating it is unable to communication with the subsystem. Is there a known workaround for this?
MAC OS-X Lion and Error 51 - Help Needed ASAP Please Hi, you cannot configure it (I guess TCP is not supported) but if the client see in Phase 1 that ESP is not working it will switch back to UDP-4500 (NAT-T). A while back, after getting "51'd" again, I went in search of a better solution -- and I found one. In Terminal, use this relatively simple command to stop and restart the kernel extension that the Error 51: Unable to communicate with the VPN subsystem. Please make sure that you have at least one network interface that is currently active and has an IP address and start this application again. Most of Internet discussions on this error message revolve around MAC OS. But this error I was able to fix on Windows XP. Normally you would be right on track - more times than not, "VPN Subsystem" problems have to do with the vpn client software not properly communicating with the operating system. Don't know if you're dealing with a "windows thing" or an environmental issue - firewall, etc. Prior to upgrading to Lion there were no issues using Cisco's VPN Client (4.9.01). With Lion, Error 51 is being returned stating it is unable to communication with the subsystem. Is there a known workaround for this? 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.
VPN client agent was unable to create the interprocess communication depot
Configure the client by going to the System Preferences > Network > Click on the “+” sign below the list of interfaces, select VPN from the interface list and Cisco IPSec from the VPN type, click create and enter your settings and your good to go.
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Cisco VPN Client Error 51 - Open Your Firewall - Domain