The machine doesn't decide that, your router does. So if the ISP says to use 1492(PPOE DSL), or 1500(PPPoA) then apply it to the router.
You can run a wireshark trace to find what is currently running
The machine doesn't decide that, your router does. So if the ISP says to use 1492(PPOE DSL), or 1500(PPPoA) then apply it to the router.
You can run a wireshark trace to find what is currently running