Firmware 8.1 Drop-in Setting Shared IP

First I apologize for the basic question but somehow is am still missing a basic configuration for the drop-in mode. I am using Balance 20X with an ISP as primary and an internal SIM card.

I have an ISP with a single IP 157.130.###.###, connected to a Linksys Router.
My internal IP gateway is, subnet

My setting in Peplink for drop-in shared IP are
Shared IP Address: 157.130.###.###
Static Route: Blank
WAN default Gateway:
DNS Servers: &

Thanks for the help

I did receive some offline help and I had a double nat from my ISP and router, makes dropin mode complicate, i have removed my second router and am now just running my peplink unit, all is working.