I have a question and searched too much could not find any solution.

I describe my scenario :

Assume I am connected with ISP Modem, from LAN port of archer I connect to TP-Link MAIN router's WAN,

From TP-Link Main router's LAN connected more 5 routers on their WAN ports.

while connected to ISP Modem I can access My TP-Link Main router WR940n But can't access all other SUB routers (already enabled remote web access of sub routers).

When connected to tplink Main router I can access all sub routers.

I want to access all sub routers (4 tplink) while I am on ISP modem.

ISP Modem : Archer C60
Main Router : WR940N
Sub routers : WR840n