I got an Asus RT-AC86U running the latest Merlin firmware and at one 1 Gigabit LAN Port i attached a 2.5G switch.
At that switch a 2.5G NAS and a 2.5G Laptop are attached.
When i am reading data from the NAS to the laptop the speed is around 300 MB/s, which is a good 2.5G speed. So far so good...