OSPF Interview Questions & Answer Part-1 | OSPF Packet Types & States

I will not explain only the theoretical concepts like in other articles or books, but my main purpose of posts is to explain & share the practical experience that I faced during project executions & implementation. I will write all interview Questions related to OSPF that will be helpful for Fresh & experienced engineers.
Below are the high-level target topics that I will explain in different parts. First interview Question then explain the summary answer of all Questions.

There are so many topics but my target is to cover those that are mostly asked in interviews & during project practical implementation.
In OSPF Part-1 I will cover The OSPF Packet types & States.
OSPF Packet Types & States Interview Questions:
Let me summarize answers of all the above Questions
There are five packet types in OSPF

The first one hello packet is used for the OSPF discovery & maintaining Neighbor relation b/w OSPF routers. I will explain the Hello packet Header in the next few posts.
DBD packet is used for the synchronization of Data bases of OSPF Routers. For example, if some new routes/Networks are added in one Router then during the DBD exchange both router routes are not the same then LRS & LSU will send & synchronize the Database.
After DBD negotiation if the Database is not synchronized, then Link state request(LSR) packet is sent for specific routes from the neighbor router then the requested records will send through Link state update. LSU contains multiple LSAs depending on LRS request.
Keep in mind that after the completion of the DBD packet successfully then LSR packet will send.
OSPF States:

If OSPF is not configured on Neighbor routers then no OSPF detection in this case OSPF state will in down state in the local Router.
When OSPF is configured on Route-A & Router-B, after configurations of Router-A. it will send a hello packet through the OSPF multicast address in this case Router-A will be in the init state means hello packet send but not received.
Then when Router-B finds the Router ID of Router-A,then it will send a hello response to Router-A in this case Router-A will be in two way state as it will receive its own router ID in the hello packet from Router-B.
Next is the exstart state in this master/slave role will be decided that will initiate communication, this role depends on large IP address not on DR or BDR.
The DBD packet is sending in the Exchange state of OSPF. If any routes are missing not same Database then LSR & LSU will send in loading state.in this state all routes best & backup will be built Database.
Now shortest path first (SFP) algorithm will be applied on the Loading state & only select the best routes from Database to make one Routing table. This is the difference b/w Loading & Full state of OSPF.
Attempt state is used in the Non-Broadcast Multi-Access (NBMA) Network type. I will explain this point in network-type articles.
In the next posts I will cover the remaining topic of OSPF, if you have any good questions in your mind I am happy to see your comments.
If you want to learn Basic Network Security & Cloud then below links for reference.