[gPXE] How to modify the code can not get DHCP information on the2nd
Shao Miller
Shao.Miller at yrdsb.edu.on.ca
Fri Nov 5 11:42:16 EDT 2010
sqwbwh wrote:
> At 2010-11-05 23:13:19,"ShaoMiller"<Shao.Miller at yrdsb.edu.on.ca> wrote:
>
> sqwbwh wrote:
>> At 2010-11-05 22:39:05,"ShaoMiller"<Shao.Miller at yrdsb.edu.on.ca>
>> wrote:
>>
>>>>>> sqwbwh wrote:
>>>>>>>
>>>>>>>
>>>>>>> How to modify the code can not get DHCP information on
>>>>>>> the 2nd?(GPXE only used to boot the system from ISCSI)
>>>>>>> Is to remove this step.
>>>>>>> net0: 00:0 c:: 29:08:11:35 on UNDI-PCI02: 01.0 (OPEN)
>>>>>>> [Link: up, TX: 0 TXE: 0 TX: 0 rxe: 0]
>>>>>>> DHCP (net0 00:0 c: 29:08:11: d5 ).... ok
>>>>>>> net0: 192.168.0.202/255.255.255.0
>>>>>>>
>>>>>>>
>>>>>>> This can speed up boot speed.
>>>>>>> Normal GPXE run to start from the boot system tftp
>>>>>>> process takes about 8 seconds or so
>>>>>>> If removed from the second time for DHCP information
>>>>>>> will only need a very quick 2.5 seconds.
>>>>>>>
>>>>> Miller, Shao wrote:
>>>>>> You most likely want the 'use-cached' option. It is DHCP gPXE encapsulated option number 178. Or, you can set it in an embedded script:
>>>>>>
>>>>>> #!gpxe
>>>>>> set use-cached 1
>>>>>> autoboot
>>>>> Gene Cumm wrote:
>>>>>>
>>>>>> What file and version are you using? It sounds as if
>>>>>> you're using
>>>>>> undionly.kpxe or a .pxe file. undionly.kkpxe will skip
>>>>>> this second
>>>>>> DHCP request but certain hardware/firmware has issues
>>>>>> with this,
>>>>>> assuming you trust the stability of your OEM's PXE/UNDI
>>>>>> stack.
>>>>>>
>>>> sqwbwh wrote:
>>>>> Shao Miller
>>>>>
>>>>> The method is successful.
>>>>> Thank you
>>>> sqwbwh wrote:
>>>>> yes
>>>>> thankyou Shao Miller
>>>>> Your method is useful :)
>>> Miller, Shao wrote:
>>>> You’re quite welcome, and thanks for including the list on
>>>> your other reply. :) Have a nice day. - Shao
>>>
>> sqwbwh wrote:
>>> Shao Miller
>>> 1:
>>> i use :
>>> " set it in an embedded script:
>>>>
>>>> #!gpxe
>>>> set use-cached 1
>>>> autoboot
>>> it's good
>>> 2:
>>> "It is DHCP gPXE encapsulated option number 178"
>>> Specifically to ask how to use this method?
>>> What can explain it in detail?
>>> thank~you
>> I enjoy using the search feature at the gPXE (Etherboot)
>> wiki. Please see:
>>
>> http://etherboot.org/wiki/doku.php?do=search&id=encapsulated&fulltext=Search
>> http://etherboot.org/wiki/msdhcp
>> http://etherboot.org/wiki/dhcpd
>>
>> ShaoMiller
>> Use the search function.
>> Use hyperlinks to provide you with three options for the
>> introduction of 178 not found.
>> 178 keyword search does not find use-cached search did not find
>> the relevant presentation.
>>
>> Hehe. Could you give me the answer it?. English is almost a maze
>> for me
>>
>
> I'm afraid that I'm not sure how to explain gPXE encapsulated
> options any better than they are explained in the wiki. DHCP
> option 175 should be a string of bytes. Within that byte sequence,
> there are sub-options. 'use-cached' is sub-option 178. So your
> DHCP option 175 could look like:
>
> 0xB2 0x01 0x01
>
> where,
>
> 0xB2 : DHCP gPXE encapsulated option 178.
> 0x01 : The encapsulated option's value occupies 1 byte.
> 0x01 : The encapsulated option's value is 1 (true).
>
> I do not know which DHCP service you use, so I do not know how you
> can reconfigure your service to give PXE clients this 'use-cached'
> option via DHCP.
>
> Shao Miller
> dhcp server is msdhcp
> Use 1781.jpg and 1782.jpg is set. Enable use-cached did not succeed
> Picture shows what can it?
Those screen-shots show a DHCP option 178, not a DHCP gPXE encapsulated
option 178.
You need DHCP option 175. _Inside_ option 175, you need to have gPXE
encapsulated option 178. See:
http://etherboot.org/wiki/msdhcp#setting_up_a_gpxe_encapsulated_options_on_windows_dhcp
It shows exactly how to create the DHCP gPXE encapsulated options. 175
is a _container_. 178 ('use-cached') goes inside that container. Change
to option 175 and you will be fine, since your bytes are exactly as I
explained above: Option 178, 1 byte long, value 1. All gPXE encapsulated
options go inside option 175. 0xB2 means 178.
Please remember to carbon-copy the list using Reply-All.
- Shao Miller
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