option 82 feature of DHCP

[Glenn Satchell]

Hi Hardik

You can use the packet() function (see dhcp-eval man page for details) but
this assumes a consistent fixed offset within the packet, otherwise no
chance without writing some C code and hacking on dhcpd itself to add a
new option to extract it.

In addition to this you can't use packet() within a host statement so
you'd need to create a class for every host. This may or may not be
practical depending on how many clients are involved.

You may just be better using mac addresses or circuit-id instead if this
is acceptable. These all work directly in host statements.

regards,
-glenn

On Mon, July 7, 2014 8:30 pm, Hardik.V.Shah at ril.com wrote:
> Hi,
>
> Sorry for the inconvenience. Please find the attached snap of serial no of
> the client box which I see through wireshark. How can I put this in
> dhcpd.conf, so that request from this box can be identified through serial
> number and assign the IP to it?
>
> Highlighted is the serial no "SGH322WF01" [below part of the image and on
> right hand side ]
>
> Thanks,
> Hardik
>
> --------------------------------------------------------------------------
>
>
> Hardik.V.Shah at ril.com wrote:
>
>> Yes, I am looking for the code which assign's the IP address based on
>> client's serial no and not mac id or circuit id or agent id.
>>
>> From the client box when dhcp request comes, I am capturing through
>> tcpdump and read through "wireshark" and able to see the serial no of
>> the box but how I can code in dhcpd.conf by which it look at that serial
>> no and assign the IP on match?
>
> You are getting the list in digest mode, can you not read the bit (which
> you've quoted below !) that says "When replying, please edit your Subject
> line so it is more specific than "Re: Contents of dhcp-users digest..."
>
> Also, please don't top post - it's intensely annoying to those of us used
> to time going forwards and where answers follow questions rather than
> preceding them. It also tends to show up as an inability to realise that
> you've included quotes of all the messages i the digest, not just the one
> little snippet you are responding to - there is no excuse for excess
> quoting other than laziness. If you can't be bothered to take a few
> seconds to do the right thing, why should everyone else reading your
> messages put the effort into working out if there's anything in all that
> irrelevant quoting that isn't irrelevant ?
>
> Now, back to your question.
> There is no standard option that would include the server serial number -
> it would be incredibly useful if there was and would have avoided a number
> of "discussions" about how to identify devices over the years. I suggest
> you post the detail of a captured packet showing the required information
> (highlight the serial number as it might not be obvious to the rest of us
> without knowledge of what's printed on a sticker on your box). Then
> someone might be able to tell you how to access and use that.
>
>
>
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