RE: [dhcwg] Server Unicast Option in DCHPv6

"Bernie Volz" <> Sat, 04 September 2004 20:38 UTC

Received: from ( []) by (8.9.1a/8.9.1a) with ESMTP id QAA06069; Sat, 4 Sep 2004 16:38:38 -0400 (EDT)
Received: from localhost.localdomain ([] by with esmtp (Exim 4.32) id 1C3hGb-0006fx-Bs; Sat, 04 Sep 2004 16:36:09 -0400
Received: from ([] by with esmtp (Exim 4.32) id 1C3hCr-0006L9-2Q for; Sat, 04 Sep 2004 16:32:17 -0400
Received: from ( []) by (8.9.1a/8.9.1a) with ESMTP id QAA05800 for <>; Sat, 4 Sep 2004 16:32:14 -0400 (EDT)
Received: from ([]) by with esmtp (Exim 4.33) id 1C3hFj-00085W-TW for; Sat, 04 Sep 2004 16:35:16 -0400
Received: from ( by with ESMTP; 04 Sep 2004 13:31:49 -0700
X-BrightmailFiltered: true
Received: from ( []) by (8.12.10/8.12.6) with ESMTP id i84KVg8J000480; Sat, 4 Sep 2004 13:31:43 -0700 (PDT)
Received: from volzw2k ( []) by (MOS 3.4.6-GR) with ESMTP id ALI20371; Sat, 4 Sep 2004 16:31:41 -0400 (EDT)
From: "Bernie Volz" <>
To: "'Suman'" <>, <>
Subject: RE: [dhcwg] Server Unicast Option in DCHPv6
Date: Sat, 4 Sep 2004 16:31:43 -0400
Organization: Cisco
Message-ID: <000c01c492be$31311bc0$>
MIME-Version: 1.0
Content-Type: text/plain; charset="US-ASCII"
Content-Transfer-Encoding: quoted-printable
X-Priority: 3 (Normal)
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook, Build 10.0.5709
In-Reply-To: <000601c49175$b2e5eaf0$>
x-mimeole: Produced By Microsoft MimeOLE V5.50.4939.300
Importance: Normal
X-Spam-Score: 0.0 (/)
X-Scan-Signature: 52f7a77164458f8c7b36b66787c853da
Content-Transfer-Encoding: quoted-printable
X-Mailman-Version: 2.1.5
Precedence: list
List-Unsubscribe: <>, <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
Content-Transfer-Encoding: quoted-printable

The unicast option is only server to client; not client to server. So, no
the client does not send the option.

There is no hard requirement for a client to use unicast. From the option
description in RFC 3315:

   The server specifies the IPv6 address to which the client is to send
   unicast messages in the server-address field.  When a client receives
   this option, where permissible and appropriate, the client sends
   messages directly to the server using the IPv6 address specified in
   the server-address field of the option.

   When the server sends a Unicast option to the client, some messages
   from the client will not be relayed by Relay Agents, and will not
   include Relay Agent options from the Relay Agents.  Therefore, a
   server should only send a Unicast option to a client when Relay
   Agents are not sending Relay Agent options.  A DHCP server rejects
   any messages sent inappropriately using unicast to ensure that
   messages are relayed by Relay Agents when Relay Agent options are in

   Details about when the client may send messages to the server using
   unicast are in section 18.

-----Original Message-----
From: [] On Behalf Of
Sent: Friday, September 03, 2004 1:20 AM
Subject: [dhcwg] Server Unicast Option in DCHPv6

      I need some clarification on the Server Unicast Option, in DHCPv6, RFC
In particular, when the client receives a Server Unicast option in an
advertise message and it has to send a request message to that server, it
unicasts the message to the server. That apart, should the client include
Server Unicast Option in the Request message that it sends? 
Also, all the subsequent transaction between the client and that server has
to be unicast, if I have got it right! Does the client need to include this
option in all the subsequent message exchanges, Request message in
Any insight into this would be greatly appreciated. 

dhcwg mailing list