asus 87u capped at 100 mb

hi all

have anyone who have a asus 87u had problem that it capped at 100mb.

i have a 400mb connection but it capped at 100mb i had this problem for ages but it really pulling my hair out bcos it does it. do asus have a auto nogation capped at 100. got a new brand new cable cat 7 into the wall to the router wan port

i have four cat 7 cable plug in to all off them 3 cable in but one swicth in a extra exten lan ports with gigabit.

is there any fix for this.? so i get my full speed for of...

asus 87u capped at 100 mb