ok Guys here is an update.
First of all thanks to all of you who pitched in to help out.
I had a chat with
Alphion guy in Chennai and told him my problem. He was very helpful. He said that
router may be need a firmware update and only MTNL can do that. Then when I mentioned about Bridged mode for using my
TP-Link to do MTU settings he told that MTNL has to do bridged mode settings from its end. User cant to do it.
Just at the end of the conversation, I mentioned to him about my TP link router being used as wifi access point. He then suggested a way to use the TP link router in dynamic IP mode.
Basically the LAN port of the
ONT Router will be connected to the WAN port of the TP Link ( Earlier I was connecting to LAN for use as an access point only which worked fine)
Then he asked to enable the DHCP on the TP Link router (I had tried this approach earlier but I had disabled the DHCP on the Alphion ONT thinking that two DHCP would lead to a problem of double NAT-as mentioned online at many places)
So basically my connection now is as follows:
Alphion ONT Router (DHCP Enabled-PPPOE Mode)-----from LAN Port-----TP Link Router (DHCP Enabled-WAN Port)-------
Android Device (Note9/
Smart TV)
I did a quick setup on the TP Link and then changed MTU settings to 1488 (found as optimum with no fragmentation)
Now all sites are working absolutely fine on both smart TV and Note 9.
NO Issues whatsover. The Alphion guy proved super helpful that too on a holiday!!!