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Visitor II
December 13, 2024
Question

UDP MTU Fragmentation on a STM32

  • December 13, 2024
  • 1 reply
  • 1251 views

I'm using the LWIP library and STM32F407. I’m trying to send a 1860 bytes  through Ethernet using UDP protocol, exceeding the Ethernet MTU (1500 bytes) so my data is fragmented. I´ve used some programs to test If I could read UDP stream, but nothing works. No problem to read packets under 1500byte (with no fragmentation) with my host application or other.. However, I can see the traffic generated by this packet using Wireshark:

MTasso_0-1734066441653.png

There is any way to read this fragmented Data properly, configuring some parameter of the LWIP library?

thanks

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    1 reply

    ST Employee
    December 13, 2024

    Hello @MTasso ,

    Ensure that the IP reassembly feature is enabled in the lwipopts.h file (#define IP_REASSEMBLY 1). This feature allows LWIP to reassemble fragmented IP packets.
    Regards

     

    MTassoAuthor
    Visitor II
    December 13, 2024

    yes it is:

    MTasso_0-1734114881209.png

     

    ST Employee
    December 30, 2024

    Hello @MTasso ,
    did you manage to get it working? if yes it would be great to share for other community users.

    if not, maybe you can check if there are any similar cases in the FreeRTOS and lwIP forum.
    Regards