Low Transfer Speeds between VLANs with CRS354 and CRS326

RouterOS Beginner Basics
1

Hi everyone,

I’m seeking some assistance with a problem I’ve been experiencing regarding low transfer speeds between VLANs on my MikroTik devices, specifically the CRS354 and CRS326 models. I have limited experience with VLANs, so any guidance or tips would be greatly appreciated.

Here’s the issue I’m facing: When my NAS and PC are in the same VLAN, the MikroTik devices utilize hardware offloading, resulting in impressive transfer speeds of around 700+ MB/s during SMB file copies. However, when I place the NAS and PC in different VLANs, the transfer rate drops drastically to only 30 MB/s.

To provide some context, here are the devices and configurations I’m using:

  • CRS354-48G-4S+2Q+: This device serves as the uplink to my router and establishes a VLAN network via the vlan-bridge. Currently, it is functioning well.
  • CRS326-24S+2Q+: This device acts as a port extender via a 40GB uplink (DAC cable). I have connected my PC and NAS to the SFP+ ports of this device.

I have followed these steps:

  • Enabled hardware offloading on the CRS354 and CRS326 using the commands:
  • /interface/ethernet/switch set 0 l3-hw-offloading=yes
    • /interface/ethernet/switch/port set [find] l3-hw-offloading=yes
  • both devices restarted

Despite these efforts, the transfer speeds remain low when the NAS and PC are in different VLANs. I have also conducted some iperf3 tests to further diagnose the issue. Here are the results:

  • different VLAN (untagged) - before enabling l3-hw-offloading=yes:
  • [ ID] Interval Transfer Bitrate Retr
    • [ 5] 0.00-10.00 sec 273 MBytes 229 Mbits/sec 2599 sender
    • [ 5] 0.00-10.04 sec 273 MBytes 228 Mbits/sec receiver
  • L3-Hardware-Offloading enabled (different VLANs, untagged):
  • [ ID] Interval Transfer Bitrate Retr
    • [ 5] 0.00-10.00 sec 273 MBytes 229 Mbits/sec 2725 sender
    • [ 5] 0.00-10.04 sec 273 MBytes 228 Mbits/sec receiver
  • L3-Hardware-Offloading enabled (same VLANs, untagged):
  • [ ID] Interval Transfer Bitrate Retr
    • [ 5] 0.00-10.00 sec 11.0 GBytes 9.41 Gbits/sec 0 sender
    • [ 5] 0.00-10.05 sec 11.0 GBytes 9.37 Gbits/sec receiver

I’m unsure of what else I could be missing or if there are additional configuration steps needed to optimize the performance.

If anyone has suggestions on how to resolve this problem, I would greatly appreciate your input. I’m open to any ideas or troubleshooting steps that might help me achieve higher transfer speeds between VLANs.

Thank you in advance for your time and assistance!

Best regards,
Matthias Schabhüttl

Edit #1: small fixes in text
Edit #2: first test is: different vlan, before enabling l3-hw-offloading

2

Oh dear.

RTFM.


Limitations
Although controller allows to configure port extender interfaces, some bridging and switching features cannot be used or will not work properly. Below are the most common controller and extender limitations. The list might change along upcoming RouterOS releases.

Feature | Support
L3HW offloading | -

As a temporary solution, I have bypassed the port extender (PE) and directly connected my devices to the CRS354.

Best Regards,
Matthias Schabhüttl