In this video we are going to discuss Trunk Negotiation. Now this is not to be confused with VTP or the VLAN Trunking Protocol although there is an aspect of VTP that does come into play when you talk about Dynamic Trunk Negotiation. In my opinion VTP was kind of misnamed, it's, it's kind of misleading because you're not really negotiating VLAN Trunks, you're really negotiating VLAN Configurations but we'll get into that when we discuss VTP elsewhere in the course. Dynamic Trunk Configuration on Cisco switches uses the Dynamic Trunking Protocol or DTP. Now DTP is Cisco proprietary protocol and it is used to determine whether or not a Switch Port will be a Trunk Port or an Access Port depending on the settings on both ends of the switches. So let's just talk about the Trunk Negotiation Settings and we'll just plow right through them here. The first is Auto and Auto means, I'll become a Trunk Port but only if you want to become a Trunk Port. I kind of get a mental image of the goofy gophers from the Warner Brothers cartoon, oh no, no after you, oh I insist you must go first, no no indubitably you have to go first. No, no after you Alphonse, anyway, if you have two switches that are set to Auto on both ends, they'll never form a trunk because their waiting for the other end to initiate trunking. Now that's something to remember if you're ever troubleshooting Dynamic Trunk Negotiation, a lot of people will say, oh well it's set to Auto, it should just auto negotiate a trunk. Well Auto doesn't really do what it says it will do or doesn't do what you think it would do and so you have to go set it to something else, namely Desirable or Dynamic Desirable. Now this is the Default Setting from most modern switches and you'll see that in the configuration when we actually set up VLANs. Desirable or Dynamic Desirable will auto negotiate as an Access Port if I don't see any DTP packets coming from the other end. Otherwise I'll negotiate as a trunk. Now Desirable or Dynamic Desirable needs to be disabled on Access Ports, this gets back to the security of the network as well as the security of the network infrastructure. If you have someone who plugs up a Cisco switch in a cube someplace and they auto negotiate a Trunk Port, then in theory they could eavesdrop on any of the VLANs that happen to cross that switch. That's not really something you want to support for any number of reasons really. The next setting is On, that's I'm a trunk, whether you like it or not. You can send me non trunk data, I'll just ignore it or more accurately I'll put in the Default VLAN. This enabled using Switch Port Mode Trunk on the Interface Configuration and we'll see that when we set up trunks in our lab. The last setting and there is one more setting but the last setting that deals with DTP is off. I'm an Access Port, whether you like it or not, you can send me tagged data, I'll just drop it. You do this by saying Switch Port Mode Access in the Interface Configuration. The last actual setting for Trunk Negotiation is not really a setting in my opinion, it's Non Negotiate and that says don't send DTP packets and ignore any that you receive. This is how you disable DTP when you're talking non Cisco equipment. Now we mentioned earlier that there was one setting in VTP that came into play when you're talking about Dynamic Trunk Configuration and that is this error message here. Unable to perform Trunk Negotiation on this port because of VTP Domain Mismatch. Now again we'll talk about VTP Domains when we discuss VTP. Basically, you'll get this message even you force the Switch Port Mode to trunk because you're still sending out those DTP packets, part of the DTP packet is the VTP Domain. The upshot of all this is you can't set up a trunk between two switches in different VTP Domains with DTP enabled even if you force them both to be Switch Port Mode Trunk, you're still trying to negotiate DTP between the two ports and so you're still seeing those packets. Basically you need to disable DTP with the Non Negotiate Setting if the two switches you're trying to set up a trunk between are in different VTP Domains. And again, as I'm wont to do, we'll actually force this error in the lab so you can actually see it in production and you can see the two ways of fixing it. Either fix VTP or disable DTP, most people disable DTP because again, you want to know where your trunks are configured, you don't want them just to set up all willy nilly all around the network. And that concludes our discussion of VLAN Trunk Negotiation.
|Course:||Implementing Cisco IP Switched Networks (642-813 SWITCH)|
|Duration:||8.5 hrs / 102 lessons|
Vista/XP/2000, OS X, Linux
QuickTime 7, Flash 8
TERMS & CONDITIONS OF USE
BY SUBSCRIBING TO THIS SERVICE, YOU ARE CONSENTING TO BE BOUND BY AND ARE BECOMING A PARTY TO THIS AGREEMENT, THE TERMS AND CONDITIONS OF WHICH SHALL PREVAIL IN GOVERNING YOUR RIGHTS OF USE. BY CLICKING THE "BECOME A MEMBER" BUTTON, THE INDIVIDUAL OR ENTITY LICENSING THE PRODUCT ("YOU") IS CONSENTING TO BE BOUND BY AND IS BECOMING A PARTY TO THIS AGREEMENT. IF LICENSEE DOES NOT AGREE TO ALL OF THE TERMS OF THIS AGREEMENT, THE BUTTON INDICATING "BECOME A MEMBER" MUST NOT BE SELECTED, AND LICENSEE MUST NOT INSTALL OR USE THE SOFTWARE.
"VTC" refers to Virtual Training Company,
"You" refers to the user or subscriber.
"Software" refers to the VTC training content and software.
2. LICENSE: VTC hereby grants to You a worldwide, non-royalty bearing, non-exclusive license to use the Software according to the provisions contained herein and subject to payment of the applicable subscription fees.
3. RESTRICTIONS: You may not do any of the following:
Save the Software to Your hard disk or other storage
medium; permit others to use the Software except as specified by addendum;
modify, reverse engineer, decompile, or disassemble the Software; make
derivative works based on the Software; publish or otherwise disseminate
the Software. VTC, Inc., VTC Online University, and the Virtual Training
Company site is owned and operated by VTC, Inc. as a corporation of
All materials on this site are the property of VTC unless otherwise specified. No material from these pages may be copied, reproduced, republished, downloaded, uploaded, posted, transmitted, or distributed in any way. Modification of the materials or use of the materials for any other purpose is a violation of U.S. copyright law and other proprietary rights. For purposes of this Agreement, the use of any such material on any other web site or networked computer environment is prohibited.
4. FEES: The rights granted under this Agreement
are effective only upon payment of the subscription fees, which are
strictly non-refundable other than as expressly provided herein. The
term "monthly subscription" is defined as any 30 day period.
The term "yearly subscription" is defined as one 365 day
period. A yearly subscription ends on the same numerical date as it
began (example July 28, 2004 to July 28, 2005).
The VTC Online University is access to every VTC training tutorial in our library. You pay a flat fee for access to these titles. You are billed according to your renewal selection below, and can renew monthly, yearly, or in any other increment offered. If you choose to be billed monthly, you will be billed every 30 days for the subscription until you request the subscription be cancelled. Our terms of service state that you must cancel a monthly subscription at least two business days before your renewal date. These two days give us enough time to ensure that you will not be charged again.
5. LIMITED WARRANTY: VTC warrants that the Software, if operated as directed, will substantially achieve the functionality described. VTC does not warrant, however, that Your use of the Software will be uninterrupted or that the operation of the Software will be error-free or secure. In addition, the security mechanisms implemented by the Software have inherent limitations, and You must determine that the Software sufficiently meets Your requirements. VTC also warrants that the media containing the Software, if provided by VTC, is free from defects in material from the date You acquired the Software. VTC's sole liability for any breach of this warranty shall be, in VTC's sole discretion: (i) to replace Your defective media or Software; or (ii) to advise You how to achieve substantially the same functionality with the Software as described; or (iii) if the above remedies are impracticable, to refund the subscription fee You paid for the Software. Only if You inform VTC of Your problem with the Software during the applicable subscription period will VTC be obligated to honor this warranty. VTC will use reasonable commercial efforts to repair, replace, advise, or refund pursuant to the foregoing warranty within thirty (30) days of being so notified. If any modifications are made to the Software by You during the warranty period; if the medium is subjected to accident, abuse, or improper use; or if You violate the terms of this Agreement, then this warranty shall immediately terminate. This warranty shall not apply if the Software is used on or in conjunction with hardware or software other than the unmodified version of hardware and software with which the Software was designed to be used as described.
THIS IS A LIMITED WARRANTY, AND IT IS THE ONLY WARRANTY MADE BY VTC OR ITS SUPPLIERS. VTC MAKES NO OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NONINFRINGEMENT OF THIRD PARTIES' RIGHTS. YOU MAY HAVE OTHER STATUTORY RIGHTS. HOWEVER, TO THE FULL EXTENT PERMITTED BY LAW, THE DURATION OF STATUTORILY REQUIRED WARRANTIES, IF ANY, SHALL BE LIMITED TO THE ABOVE LIMITED WARRANTY PERIOD. MOREOVER, IN NO EVENT WILL WARRANTIES PROVIDED BY LAW, IF ANY, APPLY UNLESS THEY ARE REQUIRED TO APPLY BY STATUTE NOTWITHSTANDING THEIR EXCLUSION BY CONTRACT. NO DEALER, AGENT, OR EMPLOYEE OF VTC IS AUTHORIZED TO MAKE ANY MODIFICATIONS, EXTENSIONS, OR ADDITIONS TO THIS LIMITED WARRANTY.
6. PROPRIETARY RIGHTS: VTC reserves all proprietary rights in and to the Software, is protected by copyright and other intellectual property laws and by international treaties. VTC, Inc.
Trademark Notice: VTC, Virtual Training Company,
Inc., The VTC Logo, and VTC Online University, are trademarks of VTC,
Inc. All other company and product names may be trademarks of their
The information contained herein is subject to change without notice. Copyright © 1995 - 2005 VTC, Inc. All rights reserved.
7. TERMINATION: This Agreement shall automatically terminate if You fail to comply with the restrictions described herein. Your obligations to pay outstanding subscription fees shall survive any termination of this Agreement.
8. LIMITATION OF LIABILITY: UNDER NO CIRCUMSTANCES
AND UNDER NO LEGAL THEORY, TORT, CONTRACT, OR OTHERWISE, SHALL VTC
OR ITS SUPPLIERS OR RESELLERS BE LIABLE TO YOU OR ANY OTHER PERSON
FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OF
ANY CHARACTER, INCLUDING WITHOUT LIMITATION, DAMAGES FOR LOSS OF GOODWILL,
WORK STOPPAGE, COMPUTER FAILURE OR MALFUNCTION, OR ANY AND ALL OTHER
COMMERCIAL DAMAGES OR LOSSES. IN NO EVENT WILL VTC BE LIABLE FOR ANY
DAMAGES IN EXCESS OF THE AMOUNT VTC RECEIVED FROM YOU FOR A LICENSE
TO THE SOFTWARE, EVEN IF VTC SHALL HAVE BEEN INFORMED OF THE POSSIBILITY
DAMAGES, OR FOR ANY CLAIM BY ANY OTHER PARTY. THIS LIMITATION OF LIABILITY SHALL NOT APPLY TO LIABILITY FOR DEATH OR PERSONAL INJURY RESULTING FROM VTC'S NEGLIGENCE TO THE EXTENT APPLICABLE LAW PROHIBITS SUCH LIMITATION. SOME JURISDICTIONS DO NOT ALLOW THE EXCLUSION OR LIMITATION OF INCIDENTAL OR CONSEQUENTIAL DAMAGES, SO THIS EXCLUSION AND LIMITATION MAY NOT APPLY TO YOU.
9. Links To Other Materials: Linked sites found at the VTC site are not under the control of VTC, and we are not responsible for the content of any linked site or any link contained in a linked site. VTC may change links based solely on our discretion, and we reserve the right to terminate any link or linking program at any time. VTC does not, by linking to sites, endorse companies or products to which it links and reserves the right to note as such on its web pages. If you decide to access any of the third party sites linked to this site, you do this entirely at your own risk.
Forums, and Chat are not always screened by VTC, and we are not responsible for the content of any public or open forum content at the site. VTC may change these public forums based solely on our discretion, and we reserve the right to terminate any forum at any time. VTC does not, by allowing these forums, endorse companies or products which may be mentioned in these forums, and reserves the right to note as such on its web pages. If you decide to access any of the public forums in this site, or linked to this site, you do this entirely at your own risk.
9. GOVERNING LAW & DISPUTE RESOLUTION: This Agreement is governed by Virginia law. All disputes between You and VTC shall be finally resolved through arbitration in Winchester, Virginia. This site is controlled by VTC from its offices within the United States of America. VTC makes no representation that materials in the site are appropriate or available for use in other locations, and access to them from territories where their content is illegal is prohibited. Those who choose to access this site from other locations do so on their own initiative and are responsible for compliance with applicable local laws. You may not use or export the Materials in violation of U.S. export laws and regulations. Any claim relating to the Materials shall be governed by the internal substantive laws of the Commonwealth of Virginia, USA.
VTC may revise these Terms at any time by updating this posting. You should visit this page from time to time to review the then-current Terms because they are binding on you. Certain provisions of these Terms may be superseded by expressly designated legal notices or terms located on particular pages at this Site.
If you have any questions regarding this policy,
or your information specifically,
you may email us at:firstname.lastname@example.org.