In the console tree of ISA Server Management, click
Virtual Private Networks (VPN).
On the Tasks tab, click Select Authentication
Methods.
On the Authentication tab, select Allow custom IPsec
policy for L2TP connection if a customer Internet Protocol
security (IPsec) policy can be used in a Layer Two Tunneling
Protocol (L2TP) VPN connection.
In Pre-shared key, type the preshared key to be used by
all connections that use this custom IPsec policy.
Notes
To open ISA Server Management, click Start, point to
All Programs, point to Microsoft ISA Server, and then
click ISA Server Management.
For ISA Server 2006 Enterprise Edition, expand
Microsoft Internet Security and Acceleration
Server 2006, expand Arrays, expand
Array_Name, and then click Virtual Private
Networks (VPN).
For ISA Server 2006 Standard Edition, expand Microsoft
Internet Security and Acceleration Server 2006, expand
Server_Name, and then click Virtual Private
Networks (VPN).
Important
For remote networks, the authentication method that you select
is the method that will be used when the remote VPN gateway
initiates a connection to the ISA Server computer.