Q on expected u-boot behavior on ping response

Dear u-boot network experts,

I'm now working on NXP MX6Q Sabreauto board with AR8031 network card. I'm using rel_imx_4.1.15_1.2.0_ga.

Basically, the network works fine. u-boot can send ping to other device, do the tftp boot as well.

But, I just realized that u-boot never respond on ping command from external device. Only the exception is that while u-boot is trying to communicate to other device via network (sending a ping command to others, or doing tftp boot, etc)

I'm not dug into detail yet.
But before doing so, I would like to confirm if this is a intentional behavior or not. I have only tried the MX6Q Sabre auto device, since this is the only device I have now.

Thanks for the feedback.

John