LSA Types 1,2 and 3
OSPF learns the topology by exchanging link-state advertisements (LSAs). In this lesson, we explain LSA Types 1, 2, and 3 in an easily understandable way.
OSPF Metric - Cost
Every dynamic routing protocol, such as OSPF, has a way to compare different paths to a destination and determine which one is best. Every protocol uses different methods of comparison based on different metric systems. OSPF uses a metric based on the outgoing interface bandwidth of each hop.
OSPF Default Route
This lesson discusses the topic of originating a default route into the OSPF network. It is a capability of the routing protocol that is very commonly used in real-world deployment and is part of the CCNA exam topics that students must be familiar with.
OSPF Passive Interface
A router often does not need to form neighbor relationships on every interface. A "passive-interface" is a network interface that participates in the OSPF routing process for advertisement purposes but does not send or receive OSPF routing updates.
Test #1 - OSPF Fundamentals
The following test is designed to confirm your understanding of the topics we have seen so far. If you have a low score, consider retaking all lessons in this section up to this point. If you pass with a high score, you can safely go to the next section.
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Lab #1. Configuring Single-Area OSPF network
After introducing the most fundamental aspects of OSPF in the previous lesson, we now start with our practical examples. This lesson demonstrates how to configure a basic single-area OSPFv2 network from scratch, walking through the most important parts of the configuration process.
OSPF DR and BDR
This lesson demonstrates the OSPF concept of a Designated Router (DR) and a Backup Designated router (BDR). We discuss why we need DR and BDR in the first place. Then, we walk through the process of electing DR and BDR on a shared segment and show some advanced examples.
How does OSPF work?
This lesson explains how OSPF works. We have broken down the OSPF operation into five steps, which we discuss at a high level.
What is OSPF?
This lesson explains what OSPF is. We introduce some of the fundamental OSPF concepts such as RID, LSA, LSDB, Adjacencies, and Areas at a high level.
Why do we need OSPF?
This lesson discusses why we need OSPF. We compare the link-state routing protocols to distance vector ones and introduce OSPF at a high level.