WSL2: Jumbo frames are not forwarded to mirrored interface on Linux

[mgkbeer]

Windows Version

Windows version: 10.0.22621.3007

WSL Version

WSL version: 2.1.0.0

Are you using WSL 1 or WSL 2?

• [ ] WSL 2
• [X] WSL 1

Kernel Version

Ubuntu-22.04

Distro Version

Ubuntu-22.04

Other Software

No response

Repro Steps

[wsl2] networkingMode = mirrored firewall=true

localhostforwarding = true

Sending Ethernet packets of size 5000 bytes. I see those on Windows but do not see those on Ubuntu's mirrored interface. I do see packets less than 1500 bytes

Expected Behavior

Expected behavior is that I do see all the packets on mirrored interface

Actual Behavior

No packets bigger the 1500 bytes are seen

Diagnostic Logs

No response

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[chanpreetdhanjal]

Hi. Can you please collect networking logs by following the instructions below? https://github.com/microsoft/WSL/blob/master/CONTRIBUTING.md#collect-wsl-logs-for-networking-issues

[Ricardo-Evans]

I also meet the same problem, is there any specific reason why WSL cannot support jumbo frames?

[arobicha]

Here's an example that captures the issue in logs.

Context is that I have AlmaLinux-9 running in WSL2 on a Windows 11 machine. Client application (192.168.42.2) is expecting 19164 jumbo packets of length 6466 or 6498 from a device on our local network (192.168.42.1). pktmon.etl captures those packets, but tcpdump does not.

WslNetworkingLogs-2025-02-04_14-52-07.zip

[randomvariable]

Can confirm that this is still the case. If folks need additional logs, let me know. Switched back to NAT mode for now.

WSL version: 2.4.13.0
Kernel version: 5.15.167.4-1
WSLg version: 1.0.65
MSRDC version: 1.2.5716
Direct3D version: 1.611.1-81528511
DXCore version: 10.0.26100.1-240331-1435.ge-release
Windows version: 10.0.26100.4202

[parallized]

I had the same issue, and I adjusting the MTU to 1500 resolved it for now.

WSL ver: 2.5.9.0
Kernel version: 6.6.87.2-1
WSLg ver: 1.0.66
MSRDC ver: 1.2.6074
Direct3D ver: 1.611.1-81528511
DXCore ver: 10.0.26100.1-240331-1435.ge-release
Windows: 10.0.26100.1742