Office laptops usually will have VPN installed.
It appears that some VPN Clients will reconfigure MTU value to 1300 bytes, presumably as a requirement of the VPN tunnel or to minimize delays.
This means that when using a TFTP server with the option negotiation ON, when U-Boot requests a packet size of 1468 bytes, the server responds by fragmenting the packets. As U-Boot does not support IP fragmentation, the transfer does not work.
To overcome this MTU on the tftp server network interface must be 1500.
You can check the MTU on a Windows PC with:
netsh interface ipv4 show subinterfaces
And if configured to something different than 1500 bytes, you can change it with:
netsh interface ipv4 set subinterface n mtu=1500 store=persistent
Where 'n' is the interface numbers as listed by the show subinterfaces option above.
Jun 13, 2019