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CCNA Certification All-In-One For Dummies by Silviu Angelescu

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Chapter 6: Open Shortest Path First (OSPF) Protocol

Exam Objectives

Describing the features and characteristics of OSPF

Describing OSPF routing decision criteria

Describing OSPF route updates and convergence

Distinguishing OSPF designated and backup designated routers

Understanding the Dijkstra shortest path first (SPF) routing algorithm

Describing OSPF route summarization

Configuring OSPF on a Cisco router

Verifying and troubleshooting OSPF on a Cisco router

OSPF is a link-state routing protocol. OSPF was developed based on an open standard and is supported by several router manufacturers. OSPF is widely used as an interior gateway protocol (IGP), especially in large network environments. Interior gateway protocols, including OSPF, route within a single routing domain. A single routing domain, also known as an autonomous system (AS), is a group of routers and network addresses that use a common routing system. For example, a network that uses OSPF on all routers is an autonomous system. This network can be connected to a large service provider network that is using another routing protocol such as IS-IS (Intermediate System–to–Intermediate System). The service provider’s IS-IS network is another autonomous system. The protocol used to route between autonomous systems and between large Internet service providers is called Border Gateway Protocol (BGP). It is not necessary to know all the details about IGPs and BGPs, but it is important to know that OSPF is classified as an interior ...

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