There is currently an issue related to the MRU of the PPPoE interface.
Some service providers use heterogeneous configuration, causing the situation when setting MTU to 1492, only some website services can be accessed (google, facebook), and many website do not access.
The way to fix the problem is to add the MRU option in the PPPoE interface.
I can bypass with options “TCP MSS Clamping for PPPoE” but if can edit MRU parameter, I can confirm that there is no need to edit TCP MSS.
Here is the example I am facing, if I rotate pppoe without fixing the default MTU and MRU is 1492.
Can access facebook and google site but another site can’t access.
And if I changed MTU 1492 and MRU 1480, I access all.