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Description of Cisco Systems' Subnet Allocation Option for DHCPv4
RFC 6656

Internet Engineering Task Force (IETF)                        R. Johnson
Request for Comments: 6656                                    K. Kinnear
Category: Informational                                         M. Stapp
ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                               July 2012

   Description of Cisco Systems' Subnet Allocation Option for DHCPv4

Abstract

   This memo documents a DHCPv4 option that currently exists and was
   previously privately defined for the operation and usage of the Cisco
   Systems' Subnet Allocation Option for DHCPv4.  The option is passed
   between the DHCPv4 Client and the DHCPv4 Server to request dynamic
   allocation of a subnet, give specifications of the subnet(s)
   allocated, and report usage statistics.  This memo documents the
   current usage of the option in agreement with RFC 3942, which
   declares that any preexisting usages of option numbers in the range
   128-223 should be documented and that the working group will try to
   officially assign those numbers to those options.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6656.

Johnson, et al.               Informational                     [Page 1]
RFC 6656         Cisco Systems' DHCP Subnet Alloc Option       July 2012

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Johnson, et al.               Informational                     [Page 2]
RFC 6656         Cisco Systems' DHCP Subnet Alloc Option       July 2012

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Subnet Allocation Option Format  . . . . . . . . . . . . . . .  5
     3.1.  Subnet-Request Suboption Format  . . . . . . . . . . . . .  5
     3.2.  Subnet-Information Suboption Format  . . . . . . . . . . .  7
       3.2.1.  Subnet Prefix Information Block Format . . . . . . . .  8
     3.3.  Subnet-Name Suboption Format . . . . . . . . . . . . . . .  9
     3.4.  Suggested-Lease-Time Suboption Format  . . . . . . . . . . 10
   4.  Requesting Allocation of a Subnet  . . . . . . . . . . . . . . 10
     4.1.  Client DHCPDISCOVER Message  . . . . . . . . . . . . . . . 11
     4.2.  Server DHCPOFFER Message . . . . . . . . . . . . . . . . . 11
     4.3.  Client DHCPREQUEST Message . . . . . . . . . . . . . . . . 12
     4.4.  Server DHCPACK Message . . . . . . . . . . . . . . . . . . 13
   5.  Client Renewal of Subnet Lease . . . . . . . . . . . . . . . . 13
     5.1.  Client RENEW DHCPREQUEST Message . . . . . . . . . . . . . 13
     5.2.  Server RENEW DHCPREQUEST Response  . . . . . . . . . . . . 14
     5.3.  Client DHCPRELEASE Message . . . . . . . . . . . . . . . . 14

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