Huawei H12-821 Exam Questions
HCIP-Datacom-Core Technology V1.0 (Page 2 )

Updated On: 12-Jun-2026

To prevent inter-area routing loops, OSPF does not allow advertising routing information between two non- backbone areas and allows advertising routing information only within an area or between the backbone area and a non-backbone area. Therefore, each ABR must be connected to the backbone area.

  1. TRUE
  2. FALSE

Answer(s): A

Explanation:

In OSPF (Open Shortest Path First), the design ensures that all non-backbone areas (e.g., Area 1, Area 2) communicate with each other only via the backbone area (Area 0). This hierarchical structure prevents routing loops between non-backbone areas.
ABR (Area Border Router): Connects one or more non-backbone areas to the backbone area.
Routing Information Flow: OSPF does not permit direct routing exchanges between two non-backbone areas. Instead, all routing information must pass through the backbone area.
This requirement ensures the integrity of routing information and avoids potential routing loops. So, every ABR must have a connection to the backbone area to facilitate this communication.



Which of the following statements regarding OSPF packets is false?

  1. DD packets contain all LSA information and can be used to periodically synchronize LSOB information between neighbors.
  2. Hello packets are used to discover and maintain OSPF neighbor relationships and also can be used to elect DR and BDR on broadcast and NBMA networks.
  3. Two routers must send Hello packets at the same interval. Otherwise, they cannot establish an OSPF neighbor relationship.
  4. DD packets carry LSA header information to describe link state summary information.

Answer(s): A

Explanation:

Database Description (DD) Packets do not contain all LSA information. Instead, they carry only the LSA headers, which are summaries of the LSAs. These summaries are used during the initial database synchronization process between OSPF neighbors to compare their LSDBs (Link-State Databases).
DD packets are not used for periodic synchronization. OSPF uses LSA flooding for this purpose when there is a change in the network.



Which of the following statements regarding OSPF neighbor relationship and adjacency is true?

  1. Not all neighbors can establish adjacencies.
  2. Neighbor relationships are selected from adjacencies to exchange routing information.
  3. OSPF routers must establish an adjacency before exchanging information.
  4. Adjacencies are maintained using OSPF DD packet

Answer(s): A

Explanation:

In OSPF, a neighbor relationship is established when two OSPF routers on the same link exchange Hello packets and pass several checks (e.g., matching area ID, authentication, and Hello/Dead intervals). However, adjacencies are established only between specific OSPF neighbors, depending on the network type and the roles of the routers:
On point-to-point and point-to-multipoint networks, all neighbors establish adjacencies.

On broadcast and NBMA networks, adjacencies are established only between a router and the DR

(Designated Router) or BDR (Backup Designated Router). Other routers maintain neighbor relationships but do not form adjacencies.



Which of the following statements regarding different LSA types is false?

  1. LS Update packets contain complete LSA information.
  2. LS Ack packets contain complete LSA information.
  3. LS Request packets contain only LS Type, LS ID, and Advertising Rooter.
  4. DD packets contain only LSA summary information, including LS Type, LS ID, Advertising Router, and LS Sequence Number.

Answer(s): B

Explanation:

LS Ack (Link-State Acknowledgment) Packets are used to acknowledge the receipt of LSAs but do not contain complete LSA information. Instead, they carry only the LSA headers to identify which LSAs are being acknowledged.



See the network shown in the following figure. Route leaking is configured on R1. In this case, R1 sends a Level-2 LSP to R3 so that R3 can learn routes on the entire network.

  1. TRUE
  2. FALSE

Answer(s): A

Explanation:

R1 is configured with import-route isis level-2 into level-1, enabling route leaking between Level-2 and Level-1 IS-IS domains.
R1, as a Level-1-2 router, performs the role of redistributing Level-2 routes into Level-1. It sends these routes as part of its Level-2 LSPs (Link-State Packets) to Level-1-only routers like R3.
This configuration allows R3, a Level-1-only router, to learn the routes of the entire network, including those in the Level-2 area, through R1.
R1 indeed sends a Level-2 LSP to R3, enabling R3 to learn routes from the whole network.



Which cost types are supported in IS-IS? (Choose all that apply.)

  1. default
  2. wide
  3. ToS
  4. Narrow

Answer(s): A,B,C,D

Explanation:

Default: This is the standard IS-IS cost metric used for path computation. It is based on a single value representing the link cost.
Wide: This metric type extends the default metric's range to accommodate modern high-speed networks, which may require larger metric values for more precise path selection. Wide metrics are part of IS-IS extensions.
ToS (Type of Service): IS-IS supports ToS-based metrics, which allow different costs to be assigned to a link for different types of traffic, although this feature is rarely used.
Narrow: This refers to the original IS-IS cost metric, which has a smaller range compared to wide metrics and is limited to values between 1 and 63. This is used in legacy IS-IS implementations.



Which of the following statements about IS-IS Hello packets are true? (Choose all that apply.)

  1. Level-1 LAN IIH packets do not contain the System ID field.
  2. P2P IIH packets and LAN IIH packets are exactly the same.
  3. P2P IIH packets do not contain the Priority field.
  4. Level-1 LAN IIH packets are sent in multicast mode.

Answer(s): C,D

Explanation:

P2P IIH packets do not contain the Priority field:
In IS-IS, the Priority field is used only in LAN IIH (Intermediate System to Intermediate System Hello) packets for the election of the Designated Intermediate System (DIS) on a broadcast network.
Point-to-Point (P2P) IIH packets do not need the Priority field because there is no DIS election in P2P networks.
Level-1 LAN IIH packets are sent in multicast mode:
LAN IIH packets are sent using multicast addresses for both Level-1 and Level-2 operations.

Specifically, Level-1 IIH packets are sent to the multicast address 01-80-C2-00-00-14.



Two Level-1 routers in different areas can establish a neighbor relationship.

  1. TRUE
  2. FALSE

Answer(s): B

Explanation:

In IS-IS, Level-1 routers can only establish neighbor relationships with other Level-1 routers within the same area.
Level-1 routers operate within a single area and do not have visibility of or communicate with routers in other areas.
If two Level-1 routers belong to different areas, they cannot form a neighbor relationship because their area IDs do not match, which is a requirement for establishing Level-1 adjacencies.



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