Server Variables Not Resolving Reliably

[MikhailCompo]

I am booting a Hyper-V guest using Tiny PXE Server.

My iPXE script starts

Code:

#!ipxe
set BootServer http://${dhcp-server}

However, BootServer and dhcp-server do not working later in the script, I always receive could not boot image, file not found.

Code:

initrd ${BootServer}/boot/BCD
initrd ${BootServer}/boot/boot.sdi
initrd ${BootServer}/sources/boot.wim

If i hard code the ip in the following then it boots fine.

Code:

initrd http://10.0.1.62/boot/BCD
initrd http://10.0.1.62/boot/boot.sdi
initrd http://10.0.1.62/sources/boot.wim

I am using a menu, and so to check the variable I use it in the Menu Title and it displays the correct http://10.0.1.62

Why are these variables not working??

iPXE 1.0.0+ (30f9)