January 8, 2012

Teaches Microsoft

BPDUGuard

As a CCNA / CCNP candidate you are expected to understand the purpose and function of Spanning-tree BPDU guard. The CCNA / CCNP's exam will ask of you to determine the purpose of the BPDUGuard (Bridge Protocol Data Unit) within the spanning-tree protocol.

Before we go into detail as to the purpose of the BPDU Guard feature a quick recap on the spanning-tree protocol is required.

Spanning-tree is a protocol which is designed to prevent physical and/or logical loops in your layer 2 network. Spanning-tree achieves this loop free environment by first of all electing a device to act as the focal point of the network which all other switches measure themselves from. This focal point role is an elected role. The election of the focal point known as the "Root Bridge" is done at the very start of spanning-tree determining the loop free topology, the election of the Root Bridge is carried out by using a combination of the switches MAC address and a value known as the "Default Priority".

These two values are conveyed into the network via BPDU's. BPDU's are used by spanning-tree to maintain a stable state network. In standard 802.1D spanning-tree for instance only the Root Bridge generated a BPDU.

The stability of the Root Bridge is of paramount importance in the operation and continual uninterrupted service of spanning-tree. A change in the position of the Root Bridge will cause service disruption on the network with data and voice session timing out.

It is important to consider what events could cause a change in the position of the Root Bridge, events such as links failing between the existing Root Bridge and the rest of the network would cause a change, or possibly a duplex mismatch between the Root Bridge and downstream switches causing the spanning-tree messages from the Root Bridge from reaching the other parts of the network. These events are easily fixed and resolved none of which would require the use of the BPDU Guard feature.

In our network we want to enforce the Spanning-tree domain borders and keep our active topology and the position of our Root Bridge predictable.

In our network we enable BPDU Guard only on access ports (access ports lead to end user devices) so that any end user devices on these ports that have BPDU Guard enabled are not able to influence the Spanning-tree topology.

BPDU Guard is enabled on an access port:

Swith(config-if)#spanning-tree bpduguard enable

Once BPDU Guard is enabled it will keep an eye open for any BPDU's entering the access ports. The only devices which can reliably create and transmit BPDU's are switches.

We want to keep a predictable topology and not allow other switches outside our control onto our network. If a rogue switch is introduced into our topology it will in most cases transmit a BPDU, if the rogue switch has "better" values than the existing Root Bridge it will cause a topology change in the switched network. Any topology change is bad news for the users.

By configuring the "BPDU Guard" feature on the access-ports enables the spanning-tree protocol to shut the port down in the event that is receives a BPDU. As a rule of thumb, BPDU's are really only expected across trunk links.

If a rogue switch is plugged into a port configured for BPDU Guard, the port will disable as soon as the first BPDU is received, by shutting the port down we prevent the rogue switch from affecting our spanning-tree topology.

To re-enable a port disabled by BDPU Guard you will need to remove the offending device and then bounce the port by issuing the shut/no shut command.

Teaches Microsoft

Are you a visual learner? Do you prefer instructions that show you how to do something - and skip the long-winded explanations? If so, then this book is for you. Open it up and you'll find clear, step-by-step screen shots that show you how to tackle more than 220 Office 2007 tasks. Each task-based spread includes easy, visual directions for performing necessary operations, including:
* Using Galleries and Live Preview
* Finding hidden files
* Creating a blog post
* Assembling and presenting slideshows
* Developing a publication
* Building a spreadsheet
* Helpful sidebars offer practical tips and tricks
* Full-color screen shots demonstrate each task
* Succinct explanations walk you through step by step
* Two-page lessons break big topics into bite-sized modules

From the Back CoverAre you a visual learner? Do you prefer instructions that show you how to do something — and skip the long-winded explanations? If so, then this book is for you. Open it up and you'll find clear, step-by-step screen shots that show you how to tackle more than 220 Office 2007 tasks. Each task-based spread includes easy, visual directions for performing necessary operations, including:

Using Galleries and Live Preview
Finding hidden files
Creating a blog post
Assembling and presenting slideshows
Developing a publication
Building a spreadsheet

Helpful sidebars offer practical tips and tricks
Full-color screen shots demonstrate each task
Succinct explanations walk you through step by step
Two-page lessons break big topics into bite-sized modules

About the AuthorSherry Kinkoph (Fishers, IN) is a freelance author and fan of all things computer related. She has written over 60 books over the past 12 years covering a variety of computer topics ranging from hardware to software, from Microsoft Office programs to the Internet. Her recent titles include Teach Yourself VISUALLY HTML, 2^nd Edition, Teach Yourself VISUALLY Office 2003, 2^nd Edition, and Teach Yourself VISUALLY Excel 2003, 2^nd Edition. Sherry worked as a manager, corporate trainer, and advertising copywriter before diving into full-time computer book authoring. A native of the Midwest, Sherry currently resides in the Indianapolis area where she continues in her quest to help users of all levels master the ever-changing computer technologies.

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39 of 39 people found the following review helpful.
Pros and Cons on Teach Yourself VISUALLY Microsoft Office 2007
By Richard P. Junghans
I found this book useful as a general overview guide to Teaching Myself VISUALLY Microsoft Office 2007. The book did not go into details in any of the sections, and it did not deal with some of the minor or advanced sections of the COMPLETE Office 2007 program, however, I do recommend it as a reasonable investment to get a quick handle on the program. It greatly helps in the transition from the old format of Office which we had from 1997 through 2003, into the new 'ribbon' format. I recommend it, but do not expect that it will answer ALL of your questions, or solve all of your change-over aches and pains. However, because I strongly believe that NOW is the time to change to a new Office system, this book is well worth the money. Go for it!

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You are better off getting the book specific to Excel, Word, etc.
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This book is too general trying to crunch very basic how-to for the entire MS Office Suite. You will find better content and tips by purchasing each book that specializes each application separately (e.g., Teach Yourself Visually Excel, Teach Yourself Visually Word, Teach Yourself Visually Outlook, etc.)

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Visual Microsoft Office 2007 text
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This book works well when you have your application open and can match book page to your window screen! Glad I ordered the online pdf file with it! Makes it even handier -- no need to cart a book around!