Questions about the TFTP protocol (arm board and virtual machine)

3. uboot uses the TFTP protocol (disable the firewall of Ubuntu and XP, and disable anti-virus software)
(1) uboot itself transplanted the Protocol to connect the network cable

The Development Board and the computer can be pinged directly.
The Development Board is connected to the vswitch, and the computer network cable is also connected to the vswitch.
The same route as the vswitch.
If the connection is wireless, You need to disconnect the wireless connection first, or click wireless-properties-remove the check box in front of the Virtual Machine (disconnect the Virtual Machine network). Do you feel that the virtual machine cannot be connected to the Internet?

(2) set the Server IP address on uboot and the IP address of the Development Board to the same network segment.
Setenv serverip 172.18.20.24
Setenv ipaddr 172.18.20.55

(3) set ethaddr (MAC address of the NIC of the Development Board)
Setenv ethaddr 00: 01: 02: 03: 04: 05
(4) Try to ping the host on the Development Board to check whether the host can be pinged.
If: Host 172.18.20.24 is alive, it is available.

Please give me more advice on any mistakes.