Using the private DHCP 224 to 254 for DHClient

Debanjan Biswas (debiswas) debiswas at cisco.com
Fri Dec 17 15:47:36 UTC 2010


Thanks a lot Glenn. I am able to retrieve the information with your
suggestions.

Regards
Debanjan

-----Original Message-----
From: dhcp-users-bounces+debiswas=cisco.com at lists.isc.org
[mailto:dhcp-users-bounces+debiswas=cisco.com at lists.isc.org] On Behalf
Of Glenn Satchell
Sent: Friday, December 17, 2010 7:00 PM
To: Users of ISC DHCP
Subject: Re: Using the private DHCP 224 to 254 for DHClient

Perhaps you did not look at this section of my earlier email:

 > The dhcp-options man page lists all the standard options. See the
 > section "DEFINING NEW OPTIONS" for the syntax to define the options
you
 > are interested in. You need to specify the type so that dhclient can
 > decode them appropriately (eg whether they are a text string,
integer,
 > IP address, etc. You need matching option definitions on the dhcp
 > server.

In your dhcpd.conf on the server there will be a definition for the type

and the name of the option number 224. You need to put that same 
definition in dhclient.conf. Then add that option name to the request 
list. I don't know how you've defined the option (whether it is a 
string, an ip address, a list of integers, etc).

It might be something like this if it is an integer, otherwise use 
exactly the same definition as in dhcpd.conf on the dhcp server:

option my-option code 224 = integer 32 ;

Then add 'request my-option' to the list for eth0.

In your dhclient script you need to decode the option and take whatever 
action is required. Use the existing option decode lines as an example 
of what is required.

regards,
-glenn

On 12/17/10 23:41, Debanjan Biswas (debiswas) wrote:
> Thanks for the info Glenn. I tried using the Request option in the
> dhclient.conf file. But, was of not much help.
>
> Below is the example of the file
>
> Interface eth0 {
> 	request subnet-mask, broadcast-address, log-server, time-offset,
> routers, domain-name, domain-name-servers;
> 	script "/sbin/dhclient-script";
> };
>
> More importantly in the DHCP server I have added a proprietary option
> 224 (which is reserved for private use). Now, I want the DHClient to
add
> this 224 option in the DHCP Discovery request? I could not get it
done.
>
> Could you please inform me how to resolve this issue.
>
> Thanking you in advance.
>
> Regards
> Debanjan
>
> -----Original Message-----
> From: dhcp-users-bounces+debiswas=cisco.com at lists.isc.org
> [mailto:dhcp-users-bounces+debiswas=cisco.com at lists.isc.org] On Behalf
> Of Glenn Satchell
> Sent: Friday, December 17, 2010 6:02 PM
> To: Users of ISC DHCP
> Subject: Re: Using the private DHCP 224 to 254 for DHClient
>
> On 12/17/10 22:02, Debanjan Biswas (debiswas) wrote:
>> Hi Everyone,
>>
>> How do I make sure that Dhclient include the private dhcp options 224
> to
>> the DHCP server in the DHCP discovery request?
>>
>> I am using DHClient version 3.0.5.
>>
>> Thanking you in advance.
>>
>> Regards
>>
>> Debanjan
>
> Have a look at the dhclient.conf man page. You probably want "also
> request" or "send".
>
> "also request" asks the server to send back the named options in the
> response. For example domain-name-servers.
>
> "send" is used to send an option to the server, such as the hostname.
>
> The dhcp-options man page lists all the standard options. See the
> section "DEFINING NEW OPTIONS" for the syntax to define the options
you
> are interested in. You need to specify the type so that dhclient can
> decode them appropriately (eg whether they are a text string, integer,
> IP address, etc. You need matching option definitions on the dhcp
> server.

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