This error indicates that the TFTP transfer has timed out.

Things to try:

• Make sure you are using the correct server address.
• Check that the TFTP server is online and responding to requests.
• Check that your IP configuration is correct. You can use the iPXE command route to show your local IP address, subnet mask, and default gateway:

    iPXE> route
    net0: 10.0.0.162/255.255.255.0 gw 10.0.0.1

• running tcpdump -s0 -vvv -i eth0 ether host [iPXE client mac] on the tftp server will show if the requests reaches the machine or not