Cisco ROUTE 2.0: Link-State Database and Optimizing OSPF Behavior

This course is included in our On-demand training solution.


OSPF as a link state protocol uses several different packets to exchange information about network topology between routers. These packets are called link-state advertisements and they describe the network topology in great detail. Each router stores the received LSA packets in the link-state database. After LSDBs are synced between the routers, OSPF uses the shortest path first algorithm to calculate the best routes. The best intra-area routes are calculated individually by each OSPF router. For the best interarea route calculation, the internal router must also rely on the best path information received from the ABRs.
Scalability, improved CPU and memory utilization, and the ability to mix small routers with large routers are all the benefits of using proper route summarization techniques. A key feature of the OSPF protocol is the ability to summarize routes at area and AS boundaries. The OSPF protocol defines several special-case area types, including stub areas, totally stubby areas, and NSSAs. The purpose of all three types of stub areas is to inject default routes into an area so that external and summary LSAs are not flooded. Default routes reduce the routing table size, and also reduce the memory and the CPU utilization. OSPF injects a default route unconditionally or based on the presence of a default route inside the routing table.
This course explains how OSPF builds the routing table. This course also defines different types of route summarization and describes the configuration commands for each type. The OSPF area types and the benefits of default routes are also described.

Target Audience

Anyone wishing to obtain real-world routing knowledge, and those that are considering CCNP and CCIP certification. This learning path’s discussion of routing could also benefit early CCIE Routing and Switching candidates. Students completing the ROUTE 2.0 learning path should have a solid foundation in routing fundamentals, Cisco IOS basics, and Cisco routing basics. Attending the ICND1 and ICND2 classes or having the CCNA certification will fulfill these expectations.



Expected Duration

150 min.

Course Objectives

Course Introduction

OSPF LSA Type Overview

  • describe different LSA types
  • OSPF LSA Type 1

  • describe functions of type 1 LSAs
  • OSPF LSA Type 2

  • describe functions of type 2 LSAs
  • OSPF LSA Type 3

  • describe functions of type 3 LSAs
  • OSPF LSA Type 4

  • describe functions of type 4 LSAs
  • OSPF LSA Type 5

  • describe functions of type 5 LSAs
  • OSPF LSA Types in the SPF Database

  • recognize LSA types in the LSBD
  • Maintaining the OSPF Database

  • recognize how OSPF maintains link-state sequence numbers
  • Synchronizing the OSPF Database

  • recognize the procedure to synchronize LSDBs
  • The DR in the OSPF Synchronization Process

  • recognize the function of the DR in the synchronization process
  • OSPF’s SPF Algorithm

  • identify how OSPF uses the OSFP algorithm
  • Best Path Selection in OSPF

  • recognize how OSPF determines link costs to calculate the best paths
  • OSPF Path Selection in a Multiarea Autonomous System

  • recognize how OSPF determines the best paths in a multiarea AS
  • Introduction to OSPF Route Summarization

  • identify the properties of OSPF route summarization
  • Interarea Route Summarization in OSPF

  • identify features of interarea route summarization
  • Summarizing on ASBRs in OSPF

  • identify how summarization can be performed for external routes
  • OSPF Area Types

  • identify OSPF area types
  • OSPF Stub Areas

  • recognize the features of stub areas
  • Configuring OSPF Stub Areas

  • configure a stub area
  • Controlling the Cost of the Default Route in Stub Areas

  • identify how the cost of a default route in stub areas can be controlled
  • OSPF Totally Stubby Areas

  • identify the features of a totally stubby area in OSPF
  • Configuring OSPF Totally Stubby Areas

  • identify the tasks that must be completed to configure an OSPF totally stubby area
  • OSPF Totally Stubby Configuration Example

  • configure an OSPF totally stubby area

  • identify characteristics of OSPF NSSAs
  • Configuring OSPF NSSAs

  • identify the features of a not-so-stubby area in OSPF
  • NSSA Configuration Example

  • configure an OSPF NSSA
  • OSPF Totally NSSAs

  • identify the features of a totally stubby area in OSPF
  • Directing Traffic Outside the AS within the OSPF AS

  • recognize how to use default routes and stub routing to direct traffic towards the Internet
  • The OSPF Default Information Originate Command

  • generate a default external route into an OSPF routing domain
  • The default-information originate Command II

  • recognize how routers use OSPF E1 and E2 external routes
  • OSPF Default Routing Example

  • select the preferred Internet service provider in a given scenario
  • Exercise: Optimizing OSPF Behavior