@Bhav In addition to what Tom posted, the server response timeout is suspicious too. IF the target computer is in uefi mode and it downloaded undionly.kpxe the target computer should have responded with something about undionly.kpxe is not the right format. But in this case its getting a server response timeout. This makes me think two things. 1) your dhcp opition 66 is set incorrectly or the name of the file has a capitalization issue. For linux Undionly.kpxe and undionly.kpxe are not the same thing. Either way I would start with your dhcp server and make sure dhcp options 66 and 67 are set correctly for a uefi based computer.
B