Dear iPXE developers,
I'm having the following problem with iPXE; I'm using the bootable ISO that I
burned to a CD-ROM.
I'm booting WinPE over PXE. This works when I'm using a DHCP server on a local
subnet (on which I can set the correct scope options), but due to security
policies I cannot set DHCP scope options on the rest of the network. So the
objective is to boot iPXE from CD-ROM or USB-key with an embedded script that
simply executes:
dhcp
set next-server x.x.x.x
imgfetch /Boot/pxeboot.n12
boot pxeboot.n12
I tested this and it works well. It doesn't work anymore though when I increase
the TFTP block size within the BCD config (so Microsoft's bootmgr.exe will
request bigger chunks of data from the TFTP-server).
Our TFTP-server must be reached over a WAN (cross-country), so TFTP-throughput
is very slow (inherent of the protocol, since it's UDP and every packet needs
to be acknowledged). On all of our PC's on the local subnet (using DHCP scope
options and the BOOT ROM of the NIC, so not iPXE) it works well when I increase
tftpblocksize to 8K and download time of a standard WinPE image drops from 10
minutes to 1,5 minute; which is great. But iPXE is unable to handle this kind
of TFTP-traffic.
Here's the script that I use to create the BCD config:
set BCD-File=C:\TFTP-ROOT\Boot\BCD
del %BCD-File%
Bcdedit /createstore %BCD-File%
Bcdedit /store %BCD-File% /create {ramdiskoptions}
Bcdedit /store %BCD-File% /set {ramdiskoptions} ramdisksdidevice boot
Bcdedit /store %BCD-File% /set {ramdiskoptions} ramdisksdipath
\boot\boot.sdi
---> Bcdedit /store %BCD-File% /set {ramdiskoptions} ramdisktftpblocksize
1432
Bcdedit /store %BCD-File% /set {ramdiskoptions} ramdisktftpwindowsize 2
Set guid={10000000-1000-1000-1000-100000000000}
Bcdedit /store %BCD-File% /create %guid% /d "WinPE PXE-boot image"
/application osloader
Bcdedit /store %BCD-File% /set %guid% systemroot \Windows
Bcdedit /store %BCD-File% /set %guid% detecthal Yes
Bcdedit /store %BCD-File% /set %guid% winpe Yes
Bcdedit /store %BCD-File% /set %guid% osdevice
ramdisk=[boot]\Boot\winpe_x86.wim,{ramdiskoptions}
Bcdedit /store %BCD-File% /set %guid% device
ramdisk=[boot]\Boot\winpe_x86.wim,{ramdiskoptions}
Bcdedit /store %BCD-File% /create {bootmgr} /d "Lite Touch
Installation"
Bcdedit /store %BCD-File% /set {bootmgr} timeout 1
Bcdedit /store %BCD-File% /set {bootmgr} displayorder %guid%
This works, but is very slow. So I replace line 7 with:
Bcdedit /store %BCD-File% /set {ramdiskoptions} ramdisktftpblocksize
8192
Now it still works on pc's using the internal NIC's PXE-boot code (and it's
much faster), but it doesn't work anymore with iPXE.
My guess is that iPXE cannot handle TFTP-responses that are spread over
multiple ethernet frames. 1432 bytes works well because with overhead it's
lower than the MTU (1500 bytes). But when the TFTP-server sends 2 or more UDP
packets (to send a bigger block of data, requiring less acknowledgements),
these somehow get lost.
Any ideas? Thanks a lot in advance.
Best regards,
Bien à Vous,
Tom Lauwers
DIGIT A.2-002 Desktop, Peripherals & Mobile Solutions
Siemens
Office: B-28 03/030
Tel. (+32-2)[29]51649 - Fax. (+32-2)[29]50164
E-mail: [email protected]
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