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DHCP Server Identifier Override Suboption
RFC 5107

Document type: RFC - Proposed Standard (February 2008)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 5107 (Proposed Standard)
Responsible AD: Jari Arkko
Send notices to: dhc-chairs@tools.ietf.org,draft-ietf-dhc-server-override@tools.ietf.org

Network Working Group                                         R. Johnson
Request for Comments: 5107                                 J. Jumarasamy
Category: Standards Track                                     K. Kinnear
                                                                M. Stapp
                                                     Cisco Systems, Inc.
                                                           February 2008

               DHCP Server Identifier Override Suboption

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This memo defines a new suboption of the DHCP relay information
   option that allows the DHCP relay to specify a new value for the
   Server Identifier option, which is inserted by the DHCP Server.  This
   allows the DHCP relay to act as the actual DHCP server such that
   RENEW DHCPREQUESTs will come to the relay instead of going to the
   server directly.  This gives the relay the opportunity to include the
   Relay Agent option with appropriate suboptions even on DHCP RENEW
   messages.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 2
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 2
   4.  Server Identifier Override Suboption Definition . . . . . . . . 3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Intellectual Property Rights and Copyright  . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 5

Johnson, et al.             Standards Track                     [Page 1]
RFC 5107              Server ID Override Suboption         February 2008

1.  Introduction

   There are many situations where a DHCP relay agent is involved, and
   it can easily insert a Relay Agent Information option [3] with
   appropriate suboptions into DHCPDISCOVER messages.  Once the lease
   has been granted, however, future DHCPREQUEST messages sent by a
   client in RENEWING state are sent directly to the DHCP server, as
   specified in the Server Identifier option.  In this case, the relay
   may not see these DHCPREQUEST messages (depending upon network
   topology) and thus cannot insert the Relay Agent Information option
   in the DHCPREQUEST messages.

   This DHCP relay agent suboption, Server Identifier Override, allows
   the relay agent to tell the DHCP server what value to place into the
   Server Identifier option [5].  Using this, the relay agent can force
   a host in RENEWING state to send DHCPREQUEST messages to the relay
   agent instead of directly to the server.  The relay agent then has
   the opportunity to insert the Relay Agent Information option with
   appropriate suboptions and relay the DHCPREQUEST to the actual
   server.  In this fashion, the DHCP server will be provided with the
   same relay agent information upon renewals (such as Circuit-ID,
   Remote-ID, Device Class, etc.) as was provided in the initial
   DHCPDISCOVER message.

   In short, this new suboption allows the DHCPv4 relay to function in
   the same fashion as the DHCPv6 relay [7] currently does.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
   document are to be interpreted as described in [1].

3.  Terminology

   This document uses DHCP terminology as defined in section 1.5 of RFC
   2131 [2], with the exception of the term "DHCP relay agent" replacing
   "BOOTP relay agent".

   Other terms used in this document:

   o  RENEW DHCPREQUEST - a DHCPREQUEST message sent by a client in
      RENEWING state

Johnson, et al.             Standards Track                     [Page 2]
RFC 5107              Server ID Override Suboption         February 2008

4.  Server Identifier Override Suboption Definition

   The format of the suboption is:

   Code   Len    Overriding Server Identifier Address
   +-----+-----+-----+-----+-----+-----+

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