In this lesson we take a look at Hello Packets and explore all the items they contain. Understanding the content of a Hello packet will show us the requirements for OSPF Routers to become Neighbors with each other.
The Hello packet also includes Area Type and BDR/DR/Priority, which allows us to explain the ideas of Stub areas and Not So Stubby Areas (NSSA). As well as the concepts of the Designated Router (DR), Backup Designated Router (BDR), and the Priority Number.
Here are all the contents of a Hello packet that are explained: Router ID, Area ID, Authentication Data, Network Mask, Hello Interval, Dead Interval, Area Type, Priority Number, Designated Router, Backup Designated Router, and Active Neighbors fields.
This is Lesson 3 of the Practical OSPF series:
https://www.youtube.com/playlist?list=PLIFyRwBY_4bSkwy0-im5ERL-_CeBxEdx3
00:00 - Start
00:12 - Hello Packet Introduction
01:43 - Router ID
02:36 - Hello Interval / Dead Interval
03:39 - Neighbors Field
05:03 - Area ID
05:18 - Authentication Data
05:51 - Network Mask
06:03 - Area Type / DR / BDR Introduction
06:19 - Normal Area, Stub Area, Not So Stubby Area (NSSA)
11:20 - Designated Router, Backup Designated Router, Priority
14:13 - When does DR/BDR election take place? Multi Access Links
15:35 - What fields must Match in Hello Packets?
17:47 - Outro
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