# Understanding the Shortest Path First (SPF) Algorithm LiveLessons (Networking Talks)

• Edition: 1st
• ISBN-10: 0-7897-5383-9
• ISBN-13: 978-0-7897-5383-0

• Description
• Sample Content

60 Minutes of Video Instruction

Understanding the Shortest Path First (SPF) Algorithm LiveLessons—Networking Talks is the primer you need to truly understand SPF calculations. It’s time to really understand how Link State protocols work and why some of the rules you encounter with this family of protocols exists.

Description

Understanding the Shortest Path First (SPF) Algorithm LiveLessons—Networking Talks explains basic SPF calculation through a combination of bullet points and whiteboard demonstrations. The lessons also demonstrate how SPF takes into account Equal-Cost MultiPath (ECMP) and multi-access links such as Ethernet. By understanding SPF calculations, engineers can better understand and troubleshoot Link State protocols.

Major sections are as follows:

Lesson 1: Overview of Distance Vector and Shortest Path First Protocols

Lesson 2: Fundamental Link State Concepts

Lesson 3: Building the Link State Database

Lesson 4: A Basic SPF Algorithm

Lesson 5: A Basic SPF Calculation

Lesson 6: Designated Routers and Pseudonodes

Lesson 7: Equal-Cost Multipath (ECMP)

Lesson 8: ECMP and Pseudonodes

Lesson 9: Problems with Link State Protocols and Conclusion

Jeff Doyle, CCIE 1919, is Principal Architect at FishNet Security. Specializing in IP routing protocols, MPLS, IPv6, SDN, and next-generation data center architectures, Jeff has designed or assisted in the design of large-scale IP service provider networks throughout North America, Europe, Japan, South Korea, Singapore, Brazil, Saudi Arabia, Australia, Taiwan, South Africa, and the People’s Republic of China. Jeff is the author of Border Gateway Protocol (BGP) LiveLessons and the best-selling Routing TCP/IP, Volume 1, both by Cisco Press.

Skill Level

• Beginner to intermediate

What You Will Learn

• An understanding of how a Link State protocol calculates a shortest path tree
• Improved understanding of the rules and behavior of Link State protocols, leading to better design and troubleshooting skills

Who Should Take This Course

Network engineers and students who want to better understand how Link State protocols work and why some of the rules they encounter with this family of protocols exist.

Course Requirements

A very basic understanding of routing protocols.

Introduction

Lesson 1: Overview of Distance Vector and Shortest Path First Protocols

Lesson 2: Fundamental Link State Concepts

Lesson 3: Building the Link State Database

Lesson 4: A Basic SPF Algorithm

Lesson 5: A Basic SPF Calculation

Lesson 6: Designated Routers and Pseudonodes

Lesson 7: Equal-Cost Multipath (ECMP)

Lesson 8: ECMP and Pseudonodes

Lesson 9: Problems with Link State Protocols and Conclusion

Lesson 1: Overview of Distance Vector and Shortest Path First Protocols

Lesson 1 provides an overview of distance vector and the shortest path first protocols so you understand the background and terminology used in the course.

Lesson 2: Fundamental Link State Concepts

Lesson 2 discusses, without going into any specific Link State protocol, essential concepts, including Adjacencies, Information Flooding, Link State Databases, and SPF Calculations.

Lesson 3: Building the Link State Database

In Lesson 3, a node-and-link network graph is drawn on the whiteboard, and the creation of a simple Link State Database based on the network is demonstrated.

Lesson 4: A Basic SPF Algorithm

Lesson 4 introduces the rules of a simple step-by-step SPF calculation.

Lesson 5: A Basic SPF Calculation

In Lesson 5, using the network and Link State Database previously drawn, an SPF calculation resulting in a loop-free, lowest-cost tree from the root to every node in the network is demonstrated.

Lesson 6: Designated Routers and Pseudonodes

SPF calculations require a graph of nodes and links. Lesson 6 discusses, using the whiteboard, how a multiaccess network such as Ethernet can be represented in such a graph.

Lesson 7: Equal-Cost Multipath (ECMP)

Lesson 7 discusses types of equal-cost paths and modifications of the SPF algorithm to support them.

Lesson 8: ECMP and Pseudonodes

A special case involving ECMP in which one of the paths crosses a pseudonode can cause an interesting calculation problem. The problem, and the SPF rule modification to prevent it, is demonstrated on the whiteboard in Lesson 8.

Lesson 9: Problems with Link State Protocols and Conclusion

Lesson 9 discusses briefly common problems in Link State networks and the features of Link State protocols that solve them. The course is then concluded.

LiveLessons Video Training series publishes hundreds of hands-on, expert-led video tutorials covering a wide selection of technology topics designed to teach you the skills you need to succeed. This professional and personal technology video series features world-leading author instructors published by your trusted technology brands: Addison-Wesley, Cisco Press, IBM Press, Pearson IT Certification, Prentice Hall, Sams, and Que. Topics include: IT Certification, Programming, Web Development, Mobile Development, Home and Office Technologies, Business and Management, and more. View all LiveLessons on InformIT at: http://www.informit.com/livelessons

Introduction

Lesson 1: Overview of Distance Vector and Shortest Path First Protocols

Lesson 2: Fundamental Link State Concepts

Lesson 3: Building the Link State Database

Lesson 4: A Basic SPF Algorithm

Lesson 5: A Basic SPF Calculation

Lesson 6: Designated Routers and Pseudonodes

Lesson 7: Equal-Cost Multipath (ECMP)

Lesson 8: ECMP and Pseudonodes

Lesson 9: Problems with Link State Protocols and Conclusion

### Submit Errata

• Accessible from your Account page after purchase. Requires the free QuickTime Player software.

Videos can be viewed on: Windows 8, Windows XP, Vista, 7, and all versions of Macintosh OS X including the iPad, and other platforms that support the industry standard h.264 video codec.

### Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.

## Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

## Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

### Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

### Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

### Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

### Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

### Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

### Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

## Other Collection and Use of Information

### Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

### Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

### Do Not Track

This site currently does not respond to Do Not Track signals.

## Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

## Children

This site is not directed to children under the age of 13.

## Marketing

Pearson may send or direct marketing communications to users, provided that

• Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
• Such marketing is consistent with applicable law and Pearson's legal obligations.
• Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
• Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

## Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

## Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

## Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

## Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

## Sharing and Disclosure

Pearson may disclose personal information, as follows:

• As required by law.
• With the consent of the individual (or their parent, if the individual is a minor)
• In response to a subpoena, court order or legal process, to the extent permitted or required by law
• To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
• In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
• To investigate or address actual or suspected fraud or other illegal activities
• To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
• To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
• To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.