This chapter focuses on a number of objectives falling under the CCNP routing principles. Understanding basic Open Shortest Path First (OSPF) routing principles not only applies to the CCNP certification but to all Cisco-based certifications. A concrete understanding of how OSPF routing works is fundamental for any small or large network. OSPF is commonly used in large service provider networks or large financial institutions. This chapter assumes knowledge of the previous chapter, which deals conceptually with IP routing principles and in particular link-state routing protocols.
The chapter starts by covering the basic OSPF concepts. It then briefly explains why OSPF is considered an improved routing protocol over Routing Information Protocol (RIP) by covering how OSPF discovers, chooses, and maintains routing tables.
Nonbroadcast multiaccess (NBMA) is a particular challenge in any network environment. This chapter covers how OSPF overcomes any limitations imposed by NBMA networks.
Five practical scenarios, included in the chapter, help you complete your understanding and ensure you have all the basic OSPF routing skills to complement your understanding of how to configure and maintain OSPF on Cisco Internet Operating System (IOS) routers.
Basic OSPF
OSPF is a link-state routing protocol. Link-state protocols use the shortest path first (SPF) algorithm to populate the routing table. OSPF shares information with every router in the network.
OSPF is considered a difficult protocol to configure and requires a thorough understanding of terms that are commonly used. Table 3-1 explains briefly the common OSPF terminology used throughout this chapter.
OSPF has so many features that the most efficient way to appreciate them is to enable OSPF on routers and observe how the routers dynamically discover IP networks.
Before covering various OSPF scenarios, this chapter covers how OSPF is configured in single and multiple OSPF areas.
The chapter starts by covering the basic OSPF concepts. It then briefly explains why OSPF is considered an improved routing protocol over Routing Information Protocol (RIP) by covering how OSPF discovers, chooses, and maintains routing tables.
Nonbroadcast multiaccess (NBMA) is a particular challenge in any network environment. This chapter covers how OSPF overcomes any limitations imposed by NBMA networks.
Five practical scenarios, included in the chapter, help you complete your understanding and ensure you have all the basic OSPF routing skills to complement your understanding of how to configure and maintain OSPF on Cisco Internet Operating System (IOS) routers.
Basic OSPF
OSPF is a link-state routing protocol. Link-state protocols use the shortest path first (SPF) algorithm to populate the routing table. OSPF shares information with every router in the network.
OSPF is considered a difficult protocol to configure and requires a thorough understanding of terms that are commonly used. Table 3-1 explains briefly the common OSPF terminology used throughout this chapter.
OSPF has so many features that the most efficient way to appreciate them is to enable OSPF on routers and observe how the routers dynamically discover IP networks.
Before covering various OSPF scenarios, this chapter covers how OSPF is configured in single and multiple OSPF areas.
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