L2TP VPN connection fails on El Capitan to Windows 2008 server. Windows 7 client works ok

Hi,

I have configured a Windows 2008 server with RRAS to allow LT2P/IPSec connections. This is working fine for clients running Windows, however no clients running OSX are able to connect.

I have checked the PPP.log and found the following.

Fri Sep 2 11:51:31 2016 : publish_entry SCDSet() failed: Success!

Fri Sep 2 11:51:31 2016 : publish_entry SCDSet() failed: Success!

Fri Sep 2 11:51:31 2016 : l2tp_get_router_address

Fri Sep 2 11:51:31 2016 : l2tp_get_router_address 172.16.31.1 from dict 1

Fri Sep 2 11:51:31 2016 : L2TP connecting to server '131.117.xxx.xx' (131.117.xxx.xx)...

Fri Sep 2 11:51:31 2016 : IPSec connection started

Fri Sep 2 11:52:01 2016 : IPSec connection failed

Please can you shine any light on why IPSec seems to fail on Mac's but not Windows machines?

Thanks,

Sam