OSPF - Neighbor Adjacencies

Question 1

What is the Hello Protocol ?

Answer 1

A protocol establishing and maintaining neighbor relationships between OSPF routers. It ensures bidirectional communication between neighbors.

Question 2

How OSPF neighbor adjacency is established ?

Answer 2

1. Hello packets are periodically sent to all OSPF routers IPv4 address 224.0.0.5
2. Adjacency is formed between two routers if they both agree on Area ID, Hello and dead interval, authentication and stub area flag. They also must be in the same IPv4 Subnet.
3. Bidirectional communication occurs when a router