Jumbo Frame problem in Bridge

RouterOS General
1

I think there is a bug in Bridge code.

I bought a NAS, so I configured MTU size 4074 (4070 for VLAN) on RB2011L, NAS and computer to get better performance.

The speed started at 45 MBps, then reduced to 5 MBps within 5 seconds. Normal speed is 35 MBps at MTU 1500.

When I decreased MTU size to 3000 at computer side, the speed began normal. above 40 MBps. CPU utilization was 45%.

Ports are bridged.

My workaround is to use switch (Master port). However, atheros8327 does not support VLAN head removal. So I have to add a managed switch.

Did anyone met the similar problem?

2

By any chance: have you the same results when you upload and download the file?

3

When I replaced RB2100L to RB250GS, transfer speed was normal. So I know it’s software bridge problem. I reconfigure it with hardware (Atheros8327) forwarding. It’s OK now. However, I lost feature below.

Can’t monitor TX/RX speed.
Can’t torch traffic.
Can’t select VLAN to attach to interface. all broadcast traffic go to slave interface.
I have to use a RB250GS to strip VLAN head.

What I get is
RB2011L CPU utilization reduced from 45% to 5% when I copy files.