Can not boot From menu file in this style

[b4us]

Hi,
I have been playing with iPXE boot system for iSCSI.
All independent startup functions can be achieved.

And the question now for me is,

this ipxe.menu File is OK, for work
#######################################
#!ipxe
set isrv 172.16.3.9
isset ${ip} || dhcp
sanboot iscsi:${isrv}::::iqn.${net0/mac:hexhyp}
#######################################

this ipxe.menu File isn't for work
#######################################
#!ipxe
isset ${ip} || dhcp
set isrv 172.16.3.9

:start
menu iPXE Boot Menu For PC:${board-serial} MAC:${mac:hexhyp}
item --gap -- --------------------------------- WIN --------------------------------
item ${mac:hexhyp} Boot From iscsi:${isrv}::::iqn.${mac:hexhyp}
item ${board-serial} Boot From iscsi:${isrv}::::${board-serial}

choose --default ${mac:hexhyp} selected
goto start

:${mac:hexhyp}
sanboot iscsi:${isrv}::::iqn.${mac:hexhyp}
exit

:${board-serial}
sanboot iscsi:${isrv}::::iqn.${board-serial}
exit

#######################################