Cubietruck: compiled U-Boot and flashed to SD card. Now it boots OK, but ethernet works weird!

[vimcoder]

 

1. Installed Armbian to SD-card-1. Booted Cubietruck from it: works great.
2. Made some changes in system and wanted that changes to another SD card, so I copied entire root ( / ) filesystem from SD-card-1 to my-armbian.tar.gz. There is better ways of doing this: dd or another make-image-software or better remember my changes related to original Armbian and made that changes in new system. But lets consider my stupid way:)
3. Got new SD card: SD-card-2. Created partition table with 1 partition. Made ext4fs on that 1 partition. Unpacked my the filesystem to the partition. Used gparted and set flag BOOT.
4. SD-card-2 didnt booted. I realized that i need U-Boot on it. So used this manual to make my SD card bootable: https://linux-sunxi.org/Bootable_SD_card#Bootloader : Git-cloned the U-Boot. cross-compiled it for default Cubieboard config.
5. dd if=u-boot-sunxi-with-spl.bin of=/dev/mmcblk-blabla bs=1024 seek=8 to SD-card-2, changed UUID in the /boot/armbianEnv.txt for UUID of newly created ext4 on step (3).
6. Now the SD-card-2 system booted OK! I see it boots by the way LED lamps blinking. Also it resets ethernet interface (it goes down then goes up) and it starts BOOTP/DHCP negotiation.

 

BUT! The weird thing happened. Ethernet works single-directional: Cubietruck do not see any packets coming to it, but everyone else see the packets coming from it. The is no thernet switches between cubieboard and the DHCP-server (my laptop), just one good ethernet cable that worked great with SD-card-1. For example, when SD-card-2 tries to get IP address using DHCP, the DHCP-server see DHCPDISCOVER and respond with DHCPOFFER, but this process has no continuation: DHCP server does not see DHCPREQUEST and following DHCPACK from the Cubieboard. The interesting thing is: when i boot this Cubieboard with the "Original" SD-card-1, everything works great. Also, when i boot some proprietary linux from NAND flash soldered to Cubieboard (i dont know what that linux does, but it talks BOOTP/DHCP after boot) the DHCP-process goes perfect too. So, i've got strange single-directional ethernet connection with my u-booted SD card and have no idea what is happening there:) Please help me understand that.