IEEE Std 802.1Q-2005(Incorporates IEEE Std 802.1Q-1998, IEEE Std 802.1u-2001,IEEE Std 802.1v-2001, and IEEE Std 802.1s-2002)I E E EStandard forLocal and metropolitan area networks Virtual Bridged Local Area Networks I E E E3 Park Avenue New York, NY10016-5997, USA19 May 2006IEEE Computer SocietySponsored by theLAN/MAN Standards CommitteeRecognized as anAmerican National Standard (ANSI)IEEE Std 802.1Q-2005(Incorporates IEEE Std 802.1Q-1998, IEEE Std 802.1u-2001,IEEE Std 802.1v-2001, and IEEE Std 802.1s-2002)IEEE Standard for Local and metropolitan area networksVirtual Bridged Local Area NetworksSponsorLAN/MAN Standards Committeeof theIEEE Computer SocietyApproved 28 March 2006American National Standards InstituteApproved 7 December 2005IEEE-SA Standards BoardThe Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY 10016-5997, USACopyright 2006 by the Institute of Electrical and Electronics Engineers, Inc.All rights reserved. Published 19 May 2006. Printed in the United States of America.IEEE and 802 are registered trademarks in the U.S. Patent & Trademark Office, owned by The Institute of Electrical andElectronics Engineers, Incorporated.Print: ISBN 0-7381-4876-6 SH95508PDF: ISBN 0-7381-4877-6 SS95508No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the priorwritten permission of the publisher.Abstract: This standard specifies how the MAC Service is supported by Virtual Bridged LocalArea Networks, the principles of operation of those networks, and the operation of VLAN-awareBridges, including management, protocols, and algorithms.Keywords: Bridged Local Area Networks, local area networks (LANs), MAC Bridges, metropolitanarea networks, Multiple Spanning Tree Protocol (MSTP), Rapid Spanning Tree Protocol (RSTP),Virtual Bridged Local Area Networks (virtual LANs)IEEE Standards documents are developed within the IEEE Societies and the Standards CoordinatingCommittees of the IEEE Standards Association (IEEE-SA) Standards Board. The IEEE develops its standardsthrough a consensus development process, approved by the American National Standards Institute, which bringstogether volunteers representing varied viewpoints and interests to achieve the final product. Volunteers are notnecessarily members of the Institute and serve without compensation. While the IEEE administers the processand establishes rules to promote fairness in the consensus development process, the IEEE does not independentlyevaluate, test, or verify the accuracy of any of the information contained in its standards.Use of an IEEE Standard is wholly voluntary. The IEEE disclaims liability for any personal injury, property orother damage, of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly orindirectly resulting from the publication, use of, or reliance upon this, or any other IEEE Standard document.The IEEE does not warrant or represent the accuracy or content of the material contained herein, and expresslydisclaims any express or implied warranty, including any implied warranty of merchantability or fitness for aspecific purpose, or that the use of the material contained herein is free from patent infringement. IEEE Standardsdocuments are supplied “AS IS.”The existence of an IEEE Standard does not imply that there are no other ways to produce, test, measure,purchase, market, or provide other goods and services related to the scope of the IEEE Standard. Furthermore, theviewpoint expressed at the time a standard is approved and issued is subject to change brought about throughdevelopments in the state of the art and comments received from users of the standard. Every IEEE Standard issubjected to review at least every five years for revision or reaffirmation. When a document is more than fiveyears old and has not been reaffirmed, it is reasonable to conclude that its contents, although still of some value,do not wholly reflect the present state of the art. Users are cautioned to check to determine that they have thelatest edition of any IEEE Standard.In publishing and making this document available, the IEEE is not suggesting or rendering professional or otherservices for, or on behalf of, any person or entity. Nor is the IEEE undertaking to perform any duty owed by anyother person or entity to another. Any person utilizing this, and any other IEEE Standards document, should relyupon the advice of a competent professional in determining the exercise of reasonable care in any givencircumstances.Interpretations: Occasionally questions may arise regarding the meaning of portions of standards as they relate tospecific applications. When the need for interpretations is brought to the attention of IEEE, the Institute willinitiate action to prepare appropriate responses. Since IEEE Standards represent a consensus of concernedinterests, it is important to ensure that any interpretation has also r