Hello

I have installed Mikrotik router with L2TP/IPSec service at some remote location and it works well when I connect through my cell mobile network (even Android phone can connect).

When I am using LAN or WLAN connection - from behind my local network setup on Mikrotik RB750G (v5.2) - and trying to connect with the same settings, L2TP can't connect. It establishes IPSec connection without problem, then L2TP negotiations didn't succeed. Firewall UDP ports 500, 1701 and 4500 are freely forwarded, as well as ipsec-esp.
Looks like Mikrotik cannot properly nat local L2TP clients connecting outside.

Please help: how to correct the local MT router/gateway to support outbound L2TP connections from local machines?

I am pretty sure somebody use L2TP/Ipsec nat'ted from behind MT for outside VPN access... plase share how it works for you.
Thank you.

Have you excluded the L2TP packets from NAT?

Regards

Andrew