Huawei H12-821 Exam Questions
HCIP-Datacom-Core Technology V1.0 (Page 10 )

Updated On: 12-Jun-2026

Which of the following statements regarding OSPF is true?

  1. OSPF does not have an acknowledgement mechanism. Therefore, OSPF relies on the upper-layer protocol,
    TCP, for acknowledgement.
  2. OSPF performs LSDB update every 30 minutes.
  3. OSPF uses the Bellman-Ford algorithm, and each router independently runs this algorithm.
  4. OSPF floods an LSU packet at an interval of 5s.

Answer(s): C

Explanation:

OSPF uses the Dijkstra algorithm (also known as SPF, Shortest Path First) for path calculation.
However, Bellman-Ford is the basis for algorithms like RIP. Despite the terminology confusion, OSPF routers independently calculate their best paths based on the Dijkstra algorithm, which is different from Bellman- Ford. This is an important distinction in routing algorithms.



Which of the following statements regarding the OSPF protocol is false?

  1. Each OSPF router uses only one Router-LSA to describe the local active connection status of an area.
  2. Routing information can be advertised only between backbone and non-backbone areas and cannot be advertised directerly between non-backbone areas.
  3. Router-LSA describes four connection types: P2P, TransNet, SubNet, and virtual link.
  4. Link State ID in a Type 3 LSA indicates the router ID of an ABR.

Answer(s): C

Explanation:

Router-LSAs (Type 1 LSAs) describe three types of connections:
1. Point-to-Point (P2P): Used for point-to-point links.
2. Broadcast (or NBMA): Used for broadcast or NBMA (Non-Broadcast Multi-Access) networks.
3. Stub (or external): For stub network connections.
The term "TransNet" does not apply to Router-LSAs, and "SubNet" and "virtual link" are not connection types for Router-LSAs. The virtual link is used for OSPF backbone connectivity, but it is not a connection type described by Router-LSAs.



This configuration is the part of RTA configuration.
Which of the following statements regarding the configuration are true? (Choose all that apply.)

[RTA]ospf 100
[RTA-ospf-100]silent-interface GigabitEthernet
/0

  1. RTA cannot establish a neighbor relationship with the neighbor that this interface is directly connected to.
  2. GigabitEthernet
    /0 is prohibited from sending OSPF packets.
  3. Direct routes of GigabitEthernet
    /0 can still be advertised.
  4. This interface cannot send Hello packets.

Answer(s): A,B,D

Explanation:

RTA cannot establish a neighbor relationship with the neighbor that this interface is directly connected to.
Since silent-interface disables OSPF Hello packet exchange, the neighbor relationship cannot be established on GigabitEthernet
/0. The OSPF process on RTA will not attempt to form an OSPF adjacency on this interface.
GigabitEthernet
/0 is prohibited from sending OSPF packets.
With the silent-interface command, OSPF packets (including Hello packets and LSAs) will not be sent on this interface, effectively prohibiting OSPF communication over it.
This interface cannot send Hello packets.
The silent-interface command specifically prevents Hello packets from being sent on the interface, which is necessary to establish OSPF neighbor relationships. As a result, OSPF Hello packets are not sent on GigabitEthernet
/0.



In the OSPF protocol, intra-area route calculation involves only Router LSA, Network LSA, and Summary LSA.

  1. TRUE
  2. FALSE

Answer(s): B

Explanation:

In OSPF (Open Shortest Path First), intra-area route calculation refers to the process of calculating routes within a single OSPF area. However, the route calculation process involves more than just the Router LSA, Network LSA, and Summary LSA.
Router LSAs (Type 1 LSAs): Describes the router's directly connected links and their states, used within the area to establish topological information.
Network LSAs (Type 2 LSAs): Generated by the Designated Router (DR) on broadcast and non-

broadcast networks, advertising the routers connected to that network.
Summary LSAs (Type 3 LSAs): These are used to advertise routes between areas, and are not used in intra-area routing. They are part of inter-area route propagation, not intra-area calculation.
For intra-area routing, the Type 1 (Router LSA) and Type 2 (Network LSA) are the key LSAs involved. Type 3 LSAs (Summary LSAs) are used for inter-area routing between different OSPF areas and do not play a role in the intra-area routing calculation.



Which of the following statements regarding OSPF multi-instance is false?

  1. Route exchange between different OSPF processes is similar to route exchange between different routing protocols.
  2. An interface of a router belongs to only a certain OSPF process.
  3. The OSPF process IDs must be the same when OSPF neighbor relationships are established between different routers.
  4. Multiple OSPF processes can run on the same router, and they are independent of each other.

Answer(s): C

Explanation:

The OSPF process ID is local to the router and is used to identify a specific OSPF process on that router.
Neighbor relationships in OSPF are not dependent on matching process IDs. As long as the routers have matching OSPF network types, area IDs, and other configuration parameters (such as authentication), OSPF neighbors can form regardless of process IDs.



In an OSPF routing domain, two routers must be specified as one DR and one BDR in a broadcast or NBMA

network with at least two routers.

  1. TRUE
  2. FALSE

Answer(s): A

Explanation:

In OSPF (Open Shortest Path First), Designated Router (DR) and Backup Designated Router (BDR) are elected on broadcast or NBMA (Non-Broadcast Multi-Access) networks to reduce the number of OSPF adjacencies and LSAs (Link-State Advertisements) exchanged, improving scalability and efficiency.
In a broadcast or NBMA network, OSPF requires one router to be elected as the DR and one as the BDR.
DR: The router that is responsible for generating and distributing LSAs for the segment.

BDR: The router that stands by in case the DR fails.

When there are at least two routers on such networks, the DR and BDR roles must be assigned. This ensures that the network can handle OSPF traffic efficiently, with the DR acting as the central point for exchanging routing information.
Key Points:
At least two routers are required for DR/BDR election.

DR and BDR are essential in broadcast and NBMA networks, but not required in point-to-point networks.

Thus, the statement is TRUE.



Four routers run IS-IS and have established adjacencies. The area IDs and router levels are marked in the following figure. R1 and R2 are connected through a PPP link, and R3 is the DIS.
Which of the following statements are true? (Choose all that apply.)

  1. If R2 sends a Level-2 LSP, R3 needs to send a PSNP for acknowledgment.
  2. R3 periodically sends CSNPs to implement Level-2 LSDB synchronization.
  3. R2 sends an LSP to R3 and R4 in unicast mode.
  4. If R1 sends an LSP, R2 needs to send a PSNP for acknowledgment.

Answer(s): A,B,D

Explanation:

If R2 sends a Level-2 LSP, R3 needs to send a PSNP for acknowledgment.
True: In IS-IS, on broadcast networks (such as the link involving R2, R3, and R4), LSP acknowledgments are achieved using Partial Sequence Number Packets (PSNPs).
When R2 sends a Level-2 LSP, R3 (the DIS) sends a PSNP as an acknowledgment.
R3 periodically sends CSNPs to implement Level-2 LSDB synchronization.
True: The DIS (Designated Intermediate System), in this case, R3, periodically sends Complete Sequence Number Packets (CSNPs) to synchronize the Level-2 Link-State Database (LSDB) on the broadcast network.
If R1 sends an LSP, R2 needs to send a PSNP for acknowledgment.
True: On the point-to-point (PPP) link between R1 and R2, IS-IS uses PSNPs for acknowledging received LSPs.



Four routers run IS-IS and have established adjacencies. The area IDs and router levels are marked in the following figure.
Which of the following statements is true?

  1. The LSDB of R2 does not contain the LSP of R4.
  2. The LSDB of R1 does not contain the LSP of R4.
  3. The LSDB of R2 does not contain the LSP of R3.
  4. The LSDB of R3 does not contain the LSP of R4.

Answer(s): B

Explanation:

In IS-IS, routers maintain separate Link-State Databases (LSDBs) for Level-1 and Level-2 areas. The behavior is based on the hierarchy and level of the routers:
1. R1 (Level-1 in Area 49.0001):
R1 is a Level-1 router and operates only within its local area (49.0001).

It does not maintain information about destinations or routers in other areas, such as Area 49.0004 where

R4 resides.
Therefore, R1's LSDB does not contain the LSP of R4.

2. R2 (Level-1-2 in Area 49.0001):
R2 is a Level-1-2 router, meaning it connects both Level-1 and Level-2 areas.

As a Level-2 router, R2 maintains LSDB entries for all Level-2 routers, including R3 and R4.

3. R3 (Level-2 in Area 49.0003):
R3 is a Level-2 router and participates in the inter-area routing of IS-IS.

It maintains LSDB entries for other Level-2 routers, including R4.

4. R4 (Level-2 in Area 49.0004):
R4 advertises its LSP to other Level-2 routers, such as R3 and R2, but not to Level-1 routers in other areas like R1.



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