Getting VPN working using L2TP with IPSEC with Forefront TMG Standard Edition
Posted on 2011-10-24
I'm working with one of my clients at the moment trying to get this working. On a Windows XP PC PPTP connections work fine but when we try to configure the VPN to use L2TP with IPSEC, the client returns error 678 “The remote computer did not respond” after a couple of minutes. The Forefront log just shows the L2TP connection being initiated and then being gracefully closed. There are some forums mentioning IP fragmentation but in the standard version of TMG there are no options to configure this. We have also tried this from a Windows 7 client and that displays a 789 "The L2TP connection attempt failed because the security layer encountered a processing error during initial negotations with the remote computer" error.
I have tried dispensing with IPSEC PSK and using a certificate instead but I get the same error. I'm running out of ideas and any pointers would be appreciated.