Add a rule to the mikrotik at 88.1 to passthrough any traffic that matches any such connection coming in and also watch its counters. Also add the two reply columns in winbox so you can see how it’s natting the connection.
I am sorry to double this question but can you access 192.168.88.150:8181 by telnet command right from 192.168.1.1 (not from LAN behind it)?
Contents of /ip firewall from both routers would be helpful.
^ this. i was supposed to have asked it in my first post
you need to test that the device or interface that receives the request from the world can route back to the intended server (and that replies go back as expected)
It is possible that 192.168.88.1 unable route packet to 192.168.1.1, but route all packet through LMT (3G modem) interface to internet. Because sync request from 192.168.1.1works Ok.
Any ideas?
You might be interested in this video at MUM about using l2tp with ipsec to achieve scalable vpn solution for both site to site and dial up road warrior scenarios.
In fact I liked it so much we are now trialling it in my own network as we get familiar with the solution for our clients. Previously we have been making static tunnels and IPSec Policy.