IPSEC automatically enables security for L2TP traffic because L2TP does NOT provide encryption.
If you wish to use pre-shared keys, see Q240262.
If you are troubleshooting L2TP/IPSEC connections, disabling the policy on both client and server will allow you to create a L2TP tunnel without IPSEC.
NOTE: Disabling IPSEC for L2TP connections limits security and should only be done when troubleshooting.
To disable the policy:
1. Use Regedt32 to navigate to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Rasman\Parameters.
2. On the Edit menu, Add Value name ProhibitIpSec, a REG_DWORD data type, and set the data value to 1.
3. Restart your Windows 2000 computer.