IPsec tunnel does not come up.

Check the logs to determine whether the failure is in Phase 1 or Phase 2.

Check the settings, including encapsulation setting, which must be transport-mode.

Check the user password.

Confirm that the user is a member of the user group assigned to L2TP.

On the Windows PC, check that the IPsec service is running and has not been disabled. See “Configuring the Windows PC”.

Tunnel connects, but there is no communication.

Did you create an ACCEPT security policy from the public network to the protected network for the L2TP clients? See “Configuring security policies”.