i need some help with setting the correct mtu size for my router, just cant seem to work it out tho using the vigor 120

modem = draytek vigor 120
router = n600
connection = PPPoE / PPPoA

i am on talktalk in the uk and if i use their router to find my max mtu through telnet i get 1492

but how would this work over the draytek PPPoE/PPPoA connection? would i still use the mtu setting of 1492 or should i subtract another 8 byte for the PPPoE header and use 1486?

you can leave it as it is if is not making any problem

You can also try 8 less but ... TT is suggesting MTU 1432 ... so do it from the n600 router if you can
I always having it at 1432 with TalkTalk as well and have NO problems