L2TP-IPSEC Fortigate-Mikrotik

Hi!

Was anybody here able to setup a working L2TP-IPSEC between a Mikrotik device as L2TP-client and a Fortigate as L2TP-server?

What I did was (first without IPSEC):

config vpn l2tp
    set eip 10.91.91.59
    set sip 10.91.91.50
    set status enable
    set usrgrp "L2TP_group"
end

→ Usergroup L2TP_group is set up.

→ L2TP-Client on Mikrotik-Device can connect and gets IP 10.91.91.51

But What is the next step to get it working? Fortigate seems to have the IP 10.91.91.50, but it is not pingable and I do not see any new interface. So how can I add IPSEC, routing, etc.?

Thank you for your help!

Stril