Interface rx limiting???

RB750 v4.2:

Interface → Ethernet → etherX → Bandwidth Rx/Tx

If you set this to 16, the error is: “min 32k supported”

So then, if you set this to 32k, the error is: “decimal number expected”

Ok, and now if you set this to 64k, the error is: “rx/tx limiting not supported on this interface”

Why is this option here then? Do ANY routerboards support limiting bandwidth directly on the interface?