So we're carrying on with our verification and configuration of Spanning Tree. We've just realized that using the Default Configuration that this Access 2 Switch, the oldest, slowest switch in the network is the Root Bridge. Obviously this is a suboptimal configuration for several reasons. Number one, the traffic flow is obviously not the most efficient which we covered in the previous video. The second reason why this is not the most efficient, is that in normal circumstances, this oldest Access 2 Switch may not have as hefty of a back plane as one of these Core Switches. Now my Core Switches happen to be 3560s which are technically also Edge Switches just like these 2950s and 2960s that are down here and for a lab, obviously I'm not going to go out and spend the money to get Nexus 7000s or 6500 series Catalysts to put up here as the core. But in a production network these Core Switches would be big, hefty, expensive Layer 3 or above switches. The back plane on these things would be multiple gigabits being able to handle multiple thousands or millions of packets per second across the back plane. This Access Switch down here probably not so much, so basically what would happen is, as users came in and started using the network and as the day wore on and you started getting more traffic going across your network, the back plane on this Access 2 Switch would get overwhelmed. You would then run the CPU up high, you'd run the buffers out and you start experiencing just general lag and general slowness on the network. You know the network would function for the most part and it would be like, you know, something's just not right with my network. It, it seems to get slower when ever people get here and start using it for the day and you can't really track down what's going on. I mean the traffics getting from Point A to Point B, it's just taking longer than I think it should but I, I can't figure out why it's taking longer. Until you go in and look at Spanning Tree and you realize well jeez, this, you know, 12 year old switch is the root of my Spanning Tree down here. So how do we rectify this? Well obviously we know that the root of Spanning Tree is the switch with the lowest Bridge ID and the Bridge ID is based on the MAC Address and the priority. Now we can't change the MAC Address or we can't change it easily. So what we have to do is lower the priority of whatever switch we want to be the root of the Spanning Tree. Now I'm going to arbitrary pick Core 2 as the root of Spanning Tree because it does actually know about this Core Router. Obviously in an actual production network, this Core Router would have an Ethernet connection to both of the Core Switches or to be even more redundant, you'd have multiple core routers going into your WAN provider. Since this is a lab, I just opted for the single Ethernet connection to keep things simple, specially since we're not going to be routing anything off, of our network. We're only concerned with the LAN here because this is the switch exam after all. So let's go up here on Core 2 and let's examine what switches are forwarding and blocking and what not on him. So let's go back to our lab PC, we'll go back to Core 2, we'll do Show Spanning Tree on this guy. We'll see that Fast Ethernet 023 is an Alternate Role. The Alternate Role basically says this is a valid Switch Port, it's up, it's connected to another switch but I can't forward traffic out of it because it would create a loop in the network and you'll see the status is in Block. And if we go back to our diagram, I'll put all those back on there. We'll see that Fast Ethernet 023 is this link between Core 2 and Core 1. So obviously since it's not the root, it picked that interface as being the one that gets to get blocked. So let's fix that. So what we'll do is, we'll go into Config Mode and let's examine some of the Spanning Tree Commands available to us. So if we do Spanning Tree and hit Question Mark, we see we've got several options, most of which we'll cover when we talk about advanced switching, that's the Backbone Fast and the Loop Guard and all these other commands. What we're looking for is the VLAN. Now even though we've not set up VLANs, the switch comes with a default VLAN or a VLAN 1 set up. If you take a switch out of the box with no configuration whatsoever and hook it up, you'll have VLAN 1 set up on all your switches. That way, you can take five Cisco switches, take them out of the box, hook them all together, hook servers and workstations and everything up to them and they'll just work with no configuration. And so that way, if you have a small network or if you're in like a disaster recovery situation where you've got set up a server farm real quick and just get some people connected to it to set up a call center for example, you could just grab and go without having to spend minutes or hours configuring all these switches. So in this case, we're going to change this Core 2's priority for VLAN 1. So we're going to do Spanning Tree VLAN 1 and we could just go manually set the priority right here and say Priority and we could say 0 to 61,440, Bridge Priority and increments of 4096. Of course the Default Priority is 32,768 or pretty much right in the middle. However there's an easier way to do it and that is to simply say Spanning Tree VLAN 1 Root. And we can say that this is the primary root or the secondary root for the Spanning Tree and this allows you to set up a little bit of redundancy in your Spanning Tree Configuration as well. This way if the primary root goes down then you know, hey if it fails, I know which switch it's going to fail to, rather than, well just pick one, because everybody else is at the Default Priority. So we'll do Spanning Tree VLAN 1 Root Primary and hit Enter and we've just called Spanning Tree to re-converge. So I'll give it a few seconds to shake itself out and then we'll look at how Spanning Tree's configured now. Now that should be more than enough time. So let's go ahead and exit Config Mode and I'll write my Config just to be on the safe side. Now if we do Show Spanning Tree, we see that this Bridge is now the root and look what it did to the priority. It lowered it to 24,577, if we had not specified that Primary Command, it would have lowered it to somewhere around 287, I think is what it could lowers it to. You'll notice that all of it's ports are now forwarding, they're all designated for the segment. There all forwarding because this is the Root Switch and that's the grand prize for winning the Root Switch election is to have all of your ports forwarding. So we'll pause here for a second and pick this up in the next video.
|Course:||Implementing Cisco IP Switched Networks (642-813 SWITCH)|
|Duration:||8.5 hrs / 102 lessons|
|Captions:||Available on CD and Online University|
WIN XP SP3, OS X 6+, Android 4, iOS 4, Linux
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.