Inter-area route calculation in OSPF involves Summary LSAs (Type 3) for summarizing routes across areas and ASBR Summary LSAs (Type 4) for locating ASBRs. While Router LSAs and Network LSAs describe the internal structure of an area, they do not directly participate in inter-area route calculation. Thus, the statement that only Router, Network, and Summary LSAs are involved is false .

OSPF routers refresh and flood LSAs in the Link-State Database (LSDB) every 30 minutes by default to maintain topology consistency. OSPF does not rely on TCP; it uses its own acknowledgment mechanism. It also uses the Dijkstra algorithm, not Bellman-Ford. The flooding interval for LSU packets is shorter, typically
5 seconds .

Hello packets are the most basic and essential type of OSPF packets used for the following purposes:
* Neighbor discovery - Routers use Hello packets to discover other OSPF routers on the same link.
* Neighbor relationship establishment - When two routers exchange matching Hello packets, they move from the "Init" state to "2-Way" and further into adjacency states.
* Neighbor relationship maintenance - Hello packets are sent periodically to ensure that neighbors are still reachable. If Hello packets are missed within the dead interval, the neighbor is considered down.
Neighbor deletion is not a direct function of Hello packets. Neighbor deletion results indirectly from missed Hello packets.
Reference:Huawei HCIP-Datacom-Core Technology Study Guide(Chapter: OSPF Fundamentals - Section:
OSPF Packet Types)

In OSPF (Open Shortest Path First), each router maintains aLink-State Database (LSDB), which must be synchronized with other routers in the same area. When an OSPF router receives anLSA (Link-State Advertisement)that it doesnot already have in its LSDB, it takes the following steps:
It updates its LSDB with the new LSA.
It floods the LSA to all its other OSPF neighbors (except the one from which it received the LSA).
This ensures that all routers in the OSPF area eventually converge to the same network topology.
Reference from Huawei HCIP-Datacom-Core Technology Study Guide:
"When an LSA is received and it is newer or not present in the LSDB, the router updates the LSDB and floods the LSA to other neighbors to ensure database synchronization." (Chapter: OSPF Fundamentals - Section: LSDB Synchronization)

R4
Explanation:
DIS Election in IS-IS:
In IS-IS, theDesignated Intermediate System (DIS)is elected on broadcast networks to reduce the number of LSAs exchanged and maintain the LSDB.
The DIS is elected based onpriority:
The router with thehighest priorityis elected as the DIS.
If priorities are equal, theSystem IDis used as a tie-breaker, and the router with thehighest System IDbecomes the DIS.
HCIP-Datacom-Core Technology Training Material (IS-IS DIS Election Mechanism).
Given DIS Priorities:
R1: Priority = 10
R2: Priority = 20
R3: Priority = 30
R4: Priority = 40
R4 has the highest DIS priority of 40, which makes it the clear choice for DIS election.
Scenario Details:
Since all devices are started simultaneously, the DIS election process will follow the priorities without requiring a tie-breaker (System ID).
Conclusion:
The device with the highest DIS priority isR4, and it will be elected as the DIS.