Customizing DHCP Configuration on the Basis of Network Topology
RFC 7969
Internet Engineering Task Force (IETF) T. Lemon
Request for Comments: 7969 Nominum, Inc.
Category: Informational T. Mrugalski
ISSN: 2070-1721 ISC
October 2016
Customizing DHCP Configuration on the Basis of Network Topology
Abstract
DHCP servers have evolved over the years to provide significant
functionality beyond that described in the DHCP base specifications.
One aspect of this functionality is support for context-specific
configuration information. This memo describes some such features
and explains their operation.
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 7841.
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/rfc7969.
Copyright Notice
Copyright (c) 2016 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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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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RFC 7969 DHCP Topology Customization October 2016
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Identifying Client's Location by DHCP Servers . . . . . . . . 3
3.1. DHCPv4-Specific Behavior . . . . . . . . . . . . . . . . 7
3.2. DHCPv6-Specific Behavior . . . . . . . . . . . . . . . . 7
4. Simple Subnetted Network . . . . . . . . . . . . . . . . . . 10
5. Relay Agent Running on a Host . . . . . . . . . . . . . . . . 12
6. Cascaded Relays . . . . . . . . . . . . . . . . . . . . . . . 12
7. Regional Configuration Example . . . . . . . . . . . . . . . 13
8. Multiple Subnets on the Same Link . . . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . 18
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
The DHCPv4 [RFC2131] and DHCPv6 [RFC3315] protocol specifications
describe how addresses can be allocated to clients based on network
topology information provided by the DHCP relay infrastructure.
Address allocation decisions are integral to the allocation of
addresses and prefixes in DHCP.
The DHCP protocol also describes mechanisms for provisioning devices
with additional configuration information, for example, DNS [RFC1034]
server addresses, default DNS search domains, and similar
information.
Although it was the intent of the authors of these specifications
that DHCP servers would provision devices with configuration
information appropriate to each device's location on the network,
this practice was never documented, much less described in detail.
Existing DHCP server implementations do in fact provide such
capabilities; the goal of this document is to describe those
capabilities for the benefit of both operators and protocol designers
who may wish to use DHCP as a means for configuring their own
services but may not be aware of the capabilities provided by most
modern DHCP servers.
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RFC 7969 DHCP Topology Customization October 2016
2. Terminology
o CPE device: Customer Premise Equipment device. Typically a router
belonging to the customer that connects directly to the provider
link.
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