Does BSP 6.x.y support TCP/IP MTU larger than 1500?

Technical Support
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1

We have an OS image built by Yocto of BSP 6.x.y. When trying to increase the MTU value of the TCP/IP configuration, we got “Invalid argument” if the MTU value is not exactly 1500 or less. The command we used was as below.

To stop the interface eth0

ifconfig eth0 down

To change the MTU

ip link set dev eth0 mtu [value]

If the value is 1500 or less, command is executed successfully. Any [value] larger than 1500 would lead to Invalid argumant error.

2

Hi, I’m the Toradex AI Assistant. The Toradex Support team will follow up with you shortly!

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Hello,

The issue you’re encountering with setting the MTU above 1500 on your Toradex device running BSP 6.x.y could be due to kernel configuration or network driver limitations. By default, many network interfaces support a standard MTU of 1500 bytes, typical for Ethernet networks.

To address this, consider the following steps:

  1. Kernel Configuration: Verify that your kernel is configured to support larger MTU sizes. Check the kernel configuration file in your Yocto project build directory for options related to network and MTU settings. Look for options like CONFIG_NET, CONFIG_INET, and any specific to your network driver that might limit MTU size.

  2. Network Driver Support: Some network drivers may have limitations on the maximum MTU they support. Review the documentation for the specific network driver used by your device to identify any such limitations.

  3. Rebuild the Kernel: If adjustments to the kernel configuration are needed, you will need to modify the configuration and rebuild the kernel:

    • Access the kernel configuration menu (e.g., using make menuconfig in the kernel source directory).
    • Adjust the relevant settings to allow for larger MTU sizes.
    • Rebuild the kernel and deploy it to your device.

  4. Testing: After making these changes, try setting the MTU again using the ip link set dev eth0 mtu <value> command to see if the issue is resolved.

I hope these steps help you resolve the issue. If you have further questions, feel free to ask.

Best regards,
Toradex AI Assistant

Please, also check if these links can help you solve your problem:

Enable Jumbo frames for ethernet?.

3

Hi @dwredx

As AI already mentioned the default MTU size is 1500 bytes. You can try to enable Jumbo frames as it discussed in this thicket Enable Jumbo frames for ethernet?

4

As well any value between 1500 and 1960?

5

By trial-and-error, it seems to be 1600 to be exact. I was not thinking about small increases. Would prefer to raise to the Ethernet adapter physical limits: [Microchip KSZ9131 Gigabit PHY] should support up to 16 KB.

6

Have you had a chance to check the thread mentioned in my previous reply?

7

Hi @dwredx ,
Any updates here?
Best regards,