I am a little confusing.
A(L2TP/IPSec VPN server ) ---- B(router) ------ (internet) ------- C(router) ------ D(client)
Can a L2TP/IPSec VPN server(A) behind NAT,serve clients(D) behind other different NATS? Can the IKE message corrected be routed to the L2TP/IPSec VPN server behind NAT?
PS: I dont have any authority to change the B router's NAT configuration. A & D can communicate with the same server who has a public IP address.