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VLAN Aggregation for Efficient IP Address Allocation (RFC3069)

IP.com Disclosure Number: IPCOM000005263D
Original Publication Date: 2001-Feb-01
Included in the Prior Art Database: 2001-Aug-20
Document File: 8 page(s) / 15K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D. McPherson: AUTHOR [+2]

Abstract

This document introduces the concept of Virtual Local Area Network (VLAN) aggregation as it relates to IPv4 address allocation. A mechanism is described by which hosts that reside in the same physical switched infrastructure, but separate virtual broadcast domains, are addressed from the same IPv4 subnet and share a common default gateway IP address, thereby removing the requirement of a dedicated IP subnet for each virtual Local Area Network (LAN) or Metropolitan Area Network (MAN).

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Network Working Group D. McPherson Request for Comments: 3069 Amber Networks, Inc. Category: Informational B. Dykes Onesecure, Inc.

February 2001

VLAN Aggregation for Efficient IP Address Allocation

Status of this Memo

This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2001). All Rights Reserved.

Abstract

This document introduces the concept of Virtual Local Area Network (VLAN) aggregation as it relates to IPv4 address allocation. A mechanism is described by which hosts that reside in the same physical switched infrastructure, but separate virtual broadcast domains, are addressed from the same IPv4 subnet and share a common default gateway IP address, thereby removing the requirement of a dedicated IP subnet for each virtual Local Area Network (LAN) or Metropolitan Area Network (MAN).

Employing such a mechanism significantly decreases IPv4 address consumption in virtual LANs and MANs. It may also ease administration of IPv4 addresses within the network.

1. Introduction

The VLAN [802.1Q] aggregation technique described in this document provides a mechanism by which hosts that reside within the same physical switched infrastructure, but separate virtual broadcast domains, may be addressed from the same IPv4 subnet and may share a common default gateway IPv4 address.

Such a mechanism provides several advantages over traditional IPv4 addressing architectures employed in large switched LANs today. The primary advantage, that of IPv4 address space conservation, can be realized when considering the diagram in Figure 1:

McPherson Dykes Informational [Page 1]

RFC 3069 VLAN Aggregation for IP Address Allocation February 2001

Figure 1:

A.1 A.2 B.1 C.1 B.2 Ethernet Switch(es)

Router

In the Figure 1 hosts A.1 and A.2 belong to customer A, VLAN A. Hosts B.1 and B.2 belong to customer B, VLAN B. Host C.1 belongs to customer C and resides in it's own virtual LAN, VLAN C.

Traditionally, an IP subnet would be allocated for each customer, based on initial IP requirements for address space utilization, as well as on projections of future utilization. For example, a scheme such as that illustrated in Table 1 may be used.

Table 1:

Gateway Usable Customer Customer IP Subnet Address Hosts Hosts A 1.1.1.0/28 1.1.1.1 14 13 B 1.1.1.16/29 1.1.1.17 6 5 C 1.1.1.24/30 1.1.1.25 2 1

Customer A's initial deployment consists of 2 hosts, though they project growth of up to 10 hosts. As a result, they're allocated the IP subnet 1.1.1.0/28 which provides 16 IP addresses. The first IP address, 1.1.1.0, represents the subnetwork number. The last IP address, 1.1.1.15, represents the directed broadcast address. The first usable address of the subnet, 1.1.1.1, is assigned to the router and serves as the default gateway IP address for the subnet. The customer is left 13 IP addresses, even though their requirement was only for 10 IP addresses.

McPherson Dykes I...