Hello, I have purchased several RB493 boards and when I try to enter an MTU higher than 1518 on an ethernet interface I get a “Couldn’t change interface - could not set mtu” message. My RouterBoard 1000 and RB500’s routers support the desired MTU of 1596 that I am looking for. I am connecting these to telephone company fiber circuits that run at 1596 MTU. Is this a bug with the RB493?
Such a big MTU is not supported on RB400 series boards.
http://wiki.mikrotik.com/wiki/Maximum_Transmission_Unit_on_RouterBoards