Thank you for your reply!
Our output of "uname -r " is “5.10.104-rt63-tegra”, which I think means that we have installed real-time kernel successfully. I think we have match the existing kernel’s configuration with last kernel. Because our NX need to boot from Nvme, which is defined in the “/boot/exlinux/exlinux.conf”. And before we change it, we even can not enter the system, which you can find the detail in Why we can't update our NX system kernel by replacing the Image in /boot/? - #3 by DaneLLL.
To be frank, I have not learned Linux systematically. So I can’t make sure what is the function of device tree and whether it can affect the connection of wired network.
So I still don’t know what is the possible reason of the wired internet loss.
And now, we use primary kernel to use internet to build the environment we need. And we find that the environment exist even if we change the image to real-time kernel. So our work can continue. But we still want to know why even the wired-internet can be affected.