Understanding LSA Group Pacing

The OSPF LSA group pacing feature allows the router to group OSPF LSAs and pace the refreshing, checksumming, and aging functions. The group pacing results in more efficient use of the router. NOTE Cisco has made LSA group pacing the default behavior for OSPF in Cisco IOS Software Each OSPF LSA is recorded and tracked with an age that indicates whether the LSA is still valid. When the LSA reaches the maximum age (60 minutes), the LSA is discarded from the link-state database. A router keeps...

Different Network Types and OSPF

There are three distinct classifications of physical network media that OSPF can differentiate between. Each of these network types requires a slightly different configuration to optimize the performance of OSPF. Configuring your OSPF network type is one of the most prominent features of OSPF. The strength of OSPF lies in its flexibility to meet certain network design requirements. The following sections show you how to customize OSPF to your network's design. Cisco IOS Software allows five...

Link State Versus Distance Vector Routing Protocols

This section describes the two most common and relevant routing protocols that TCP IP has available for use, namely RIP and OSPF. Controversy surrounds the debate over link-state versus distance vector routing algorithms regarding which is better. NOTE Link-State and distance vector routing protocols are also known as interior gateway protocols (IGPs) this concept is discussed later in the discussion of OSPF and border gateway protocol (BGP) interoperability. Chapter 7, Summarization, discusses...

Understanding the Seven Layers of the OSI Reference Model

Osi Reference Model Layers

The seven layers of the OSI reference model can be divided into two categories upper layers and lower layers. The upper layers are typically concerned only with applications, and the lower layers primarily handle data transportation. The sections that follow examine the three upper layers, the four lower layers, and the functions of each. The upper layers of the OSI reference model 5, 6, and 7 are concerned with application issues. They are generally implemented only in software programs. The...

Neighbor Stuck in Init STATE

The init state indicates that a router sees Hello packets from the neighbor, but two-way communication has not been established. A Cisco router includes the router IDs of all neighbors in the init (or higher) state in the neighbor field of its Hello packets. Example 3-15 shows sample output of the show ip ospf neighbor command. Example 3-15 Output from the show ip ospf neighbor Command For two-way communication to be established with a neighbor, a router must also see its own router ID in the...