DHCP option 26 (MTU)

[Glenn Satchell]

If a particular client doesn't request an option, then even though you 
force the client to request that option, the client may still ignore it 
or not know how to configure that option.

regards,
-glenn

On 11/03/11 01:50, Carl Williams wrote:
>
> Hi All,
>
>
>    I have set the DHCP Client to request option 26 and configured an ISC
> DHCP server to respond with DHCP 26 with specified MTU.
>
>    I used a MAC OS version 10.6.4 and added option 26 to the default list
> for dhcp client to request in the file:
> /System/Library/SystemConfiguration/IPConfiguration.bundle/Contents/Resourc
> es/IPConfiguration.xml
>
>
>     My MACBOOK Air (Lion) has no such file and I can't figure out how to do
> it on the Lion OS.
>
>     But on the MACOS 10.6.4 I can see from the wireshark files that option
> 26 with the MTU that I set in server is in fact
> Being sent via DHCP OFFER and DHCP ACK.  But the interface that DHCP is
> configured on - en0 - is not setting the MTU as specified according
> To the DHCP response.
>
>
>     I am wondering what OS have what behavior and handle this option.  This
> is not so clear.
>
>     I also want information on how to set this on Windows 7 or some version
> of windows - the registry setup is complicated and I tried it
> But no MTU request (option 26) is being made by the windows box despite me
> setting up a registry key for option 26 for dhcp.  Perhaps I need
> To trigger it some how or do some extra stuff there - not sure.
>
>    But also any other information on dhcp option 26 on any os would be
> useful.
>
> Carl
>
>
> On 11/2/11 7:32 AM, "Ralph Droms"<rdroms at cisco.com>  wrote:
>
>> I would be interested to hear if receiving DHCP option 26 has an effect
>> on the interface MTU; i.e., are there any clients that actually process
>> DHCP option 26 and make the appropriate change to the interface settings
>> through the client OS.
>>
>> - Ralph
>>
>> On Nov 1, 2011, at 4:00 PM 11/1/11, Carl Williams wrote:
>>
>>>
>>>
>>> I wish to have my MACOS (Macbook Air) request the DHCP option 26 for
>>> setting MTU.  How can I change the default MACOS (LION) dhcp options to
>>> do this?
>>>
>>> Also if you have same to add this option 26 to windows 7 as well?
>>>
>>> Carl
>>>