sorry for that silly question and my bad grammar, i have tried to configure L2TP with IPSec on this topology but i still can't activate the IPSec on the router. the L2TP tunnel is worked properly, but when i add an IPSec, the tunnel still worked with no IPSec running.

i use this configuration on gateway router

/ip ipsec proposal
set [ find default=yes ] enc-algorithms=3des,aes-128,aes-192,aes-256
/ip ipsec peer
add generate-policy=yes hash-algorithm=sha1 nat-traversal=yes secret=test123456 send-initial-contact=no

i use RouterOS v4.3
my client is windows 7 home premium

what should i do next?
thank you.

i use RouterOS v4.3 ... what should i do next?

Upgrade to ROS 5.x.

i use RouterOS v4.3 ... what should i do next?

Upgrade to ROS 5.x.

is it necessary? because I don't have any privilege to do that...
so, it would be a dead end, is it?

i use RouterOS v4.3 ... what should i do next?

Upgrade to ROS 5.x.

is it necessary? because i don't have privilege to do that.

is it necessary? because i don't have any privilege to do that.

is it necessary? because i don't have any privilege to do that.

4.3 is incredibly old. Assuming that you have read the wiki section on IPSec and have set your configuration correctly, then this would be my first course of action.

If client is windows PC then you need to set exchange mode to main-l2tp which is available starting from v5.4