I don't think 122.176.0.0/24 is the issue because I was using this series 1 week ago and it was working fine. Well, just had a talk with local engineer and the backend guy, they said there is some issue with the IP assigned to me 2 days ago and they are cancelling it and putting up a request for a new one.
Correct, gateway with PPPoE is 122.161.47.255
Let's see what happens, I keep the thread updated.