How to configure dhclient to send option#82

[Jeff Waller]

Usually the OLT can be configured to modify the contents of the DHCP packets
to include option 82.  Check with vendor.
 
On Feb 5, 2012, at 7:11 AM, David Ganor wrote:

> Hi Niall,
> Well, without going into too many details...
> 1. The system is a control host for a DPoE (DOCSIS Provisioning over EPON)
> network:
> 	a. the DPoE-system is a Linux machine connected to an EPON manager
> box, called an OLT.
> 	b. The OLT manages/controls an EPON optical network, in which each
> node is terminated by a remote "MODEM", called an ONU.
> 	c. The ONU services network devices, such as computers, VOIP phones,
> set-top boxes etc. These devices run an IP stack and needs to get an IP
> address from a DHCP server.
> 	d. An ONU doesn't run an IP stack, but is managed via SNMP, through
> an agent running on the system.
> 2. The system runs DHCP clients to get IP addresses for managed entities
> (ONUs) and also acts as a DHCP relay, on behalf of non-managed, remote
> devices.
> 3. Whenever a managed entity is connected and the associated SNMP agent
> requests an IP address, it should also add option#82-suboption#9 with
> enterprise number 4491 (indicating CabelLabs Inc., the owner of the DPoE and
> DOCSIS specs)
> 4. The dhcrelay, as a standalone process, can probably be used for the phase
> of getting the IP address, but doing the actual relaying job between 2
> interfaces, on separated IP subnets is not feasible:
> the DHCP messages from, and to, the non-managed remote devices don't go
> through a "regular" (Linux) Ethernet interface - it's a special host-control
> interface with a special control application (which we develop...)
> 
> I hope this not-so-short-after-all background overview makes my question a
> little clearer, so to summarize:
> Can I, somehow, run/connect/configure something(s) so that the DHCPDiscover
> and DHCPRequest will include this option#82?
> 
> I know I can hard-code this option in the dhclient and re-build the
> executable, but I would prefer not to...
> 
> 
> Thak you for yout time,
> David Ganor
> 
> 
> -----Original Message-----
> From: dhcp-users-bounces+david=oliver-solutions.com at lists.isc.org
> [mailto:dhcp-users-bounces+david=oliver-solutions.com at lists.isc.org] On
> Behalf Of Niall O'Reilly
> Sent: Thursday, February 02, 2012 11:58 AM
> To: Users of ISC DHCP
> Subject: Re: How to configure dhclient to send option#82
> 
> 
> On 2 Feb 2012, at 07:51, David Ganor wrote:
> 
>> I need to configure a dhclient to send option#82 with a specific
> sub-option #9 in the DHCPDiscover and in the DHCPRequest messages.
> 
> 	I believe that that's a need which is architecturally beyond what
> DHCP
> 	is intended for.
> 
> 	Option 82 is intended to be used for adding information to the DHCP
> 	exchange which is available on the relay device (usually a router),
> 	but not on the client.  By design, a client simply doesn't do option
> 82.
> 
> 	From what you say, it appears to me that you need to communicate
> some
> 	property of the client to the server, and that this property is
> known 
> 	(by configuration) at the client.  I think you should best choose an
> 	appropriate option from among those that the client con be
> configured
> 	to send.
> 
> 	Without further information about what you are actually trying to
> 	achieve, and perhaps also about your network topology, it will be
> 	difficult for anyone on the list to give you advice relevant to
> 	your circumstances.
> 
> 
> 	Best regards,
> 	Niall O'Reilly
> 
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