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.
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.
OSPF LSA Type Overview
OSPF LSA Type 1
OSPF LSA Type 2
OSPF LSA Type 3
OSPF LSA Type 4
OSPF LSA Type 5
OSPF LSA Types in the SPF Database
Maintaining the OSPF Database
Synchronizing the OSPF Database
The DR in the OSPF Synchronization Process
OSPF’s SPF Algorithm
Best Path Selection in OSPF
OSPF Path Selection in a Multiarea Autonomous System
Introduction to OSPF Route Summarization
Interarea Route Summarization in OSPF
Summarizing on ASBRs in OSPF
OSPF Area Types
OSPF Stub Areas
Configuring OSPF Stub Areas
Controlling the Cost of the Default Route in Stub Areas
OSPF Totally Stubby Areas
Configuring OSPF Totally Stubby Areas
OSPF Totally Stubby Configuration Example
Configuring OSPF NSSAs
NSSA Configuration Example
OSPF Totally NSSAs
Directing Traffic Outside the AS within the OSPF AS
The OSPF Default Information Originate Command
The default-information originate Command II
OSPF Default Routing Example
Exercise: Optimizing OSPF Behavior