Does someone did testing for the Etherent reliability can be reference ? I test it with demo code . I use SmartBits to snet out the 100Byes packet per 20us. And I ping from other computer for monitor the reply status. Once I start to sent the packet from SmartBits, it will make Ethernet not reply anymore. I did testing for simple code with uIP, it works normal. Does someone meet same problem or have any idea for fix this problem.

Which MCU are you using?

I am using STR912FW47-6 MCU with STE-100P PHY

What does ethernet have to do with FreeRTOS? FreeRTOS does not provide ethernet functionality. There are some demos but then you’re probably asking the question in the wrong place if it’s a uIP (or whatever) specific question.