@rakib386 the solution works as long as the router for the main access point doesn't change the WiFi channel number. I think it is better to mention that point as a note. In my case the service provider (Airtel) has modified the firmware so that the channel number selections cannot be made fixed In such case (i.e., it is always set to 'Auto'). In this configuration, if I power on and power off the main router, then the repeater stops working, and I need to re-do everything!