Free Huawei H12-821_V1.0 Practice Exam with Questions & Answers | Set: 3

Comprehensive and Detailed in-depth Step-by-Step Explanation:

In OSPF, Link State Advertisements (LSAs) are used to exchange routing and topology information. Each LSA in the OSPF network is uniquely identified using a 3-tuple identifier , which consists of:

Link State ID :

The Link State ID uniquely identifies the LSA within the OSPF area. Its value depends on the LSA type. For example, for a Router LSA, the Link State ID is the originating router’s Router ID.

Advertising Router :

This is the Router ID of the router that generated the LSA. It identifies which router is responsible for creating and advertising this LSA.

LSType :

This field identifies the type of LSA (e.g., Router LSA, Network LSA, Summary LSA, AS-External LSA, etc.). It is crucial for interpreting the purpose and content of the LSA.

The LS Sequence Number is not part of the 3-tuple that uniquely identifies the LSA. Instead, it is used to determine the most recent version of the LSA in case there are multiple instances of the same LSA.

BFD (Bidirectional Forwarding Detection) is a lightweight protocol that provides rapid detection of faults in the forwarding path between two routers or switches.

It works in conjunction with routing protocols and provides fast failure detection to enable quick route convergence.

Protocol support:

B. BFD for static routes – Supported. BFD tracks the reachability of next-hop addresses and can trigger route removal upon failure.

C. BFD for OSPF – Supported. BFD can be associated with OSPF to accelerate the detection of neighbor failures.

D. BFD for BGP – Supported. BFD enables sub-second detection of BGP peer failures.

A. BFD for PIM – Not supported . PIM (Protocol Independent Multicast) typically does not use BFD for neighbor failure detection.

Reference from Huawei HCIP-Datacom-Core Technology Study Guide:

“BFD can be associated with static routes, OSPF, IS-IS, BGP, and other protocols to quickly detect link or device faults and trigger fast rerouting.”

(Chapter: High Availability Technologies – Section: BFD Principles and Applications)

Comprehensive and Detailed In-Depth Explanation:

OSPF network types affect how protocol packets (Hello, LSA updates) are transmitted:

NBMA (Non-Broadcast Multi-Access) networks (e.g., Frame Relay) do not support multicast , so routers must unicast OSPF packets to neighbors.

Broadcast networks (e.g., Ethernet) support multicast and use 224.0.0.5 for Hello packets and 224.0.0.6 for DR/BDR communication .

The statement is false because:

NBMA does not unicast all packets —only Hello packets must be manually configured to be unicast.

LSAs and routing updates can still be multicast if an NBMA network is configured as point-to-multipoint .

???? Reference: Huawei HCIA-Datacom Study Guide, OSPF Network Types and Packet Transmission.

Comprehensive and Detailed In-Depth Explanation:

Intermediate System to Intermediate System (IS-IS) routers send IS-to-IS Hello (IIH) packets to establish neighbor relationships.

The Reserved/Circuit Type field in IIH packets indicates which level of IS-IS adjacency the router is trying to establish:

00 → Level-0 (Not used in IS-IS).

01 → Level-1 router.

10 → Level-2 router.

11 → Level-1-2 router (Both levels supported) .

Since the question asks for the field value in an L1-L2 router’s IIH packets , the correct answer is 11 (B) .

???? Reference: Huawei HCIA-Datacom Study Guide, IS-IS Neighbor Discovery and IIH Packet Format.

Understanding the LSDB and Level-2 DIS Election in IS-IS :

In IS-IS, the Designated Intermediate System (DIS) is elected for both Level-1 and Level-2 on broadcast networks to manage the link-state database (LSDB) and reduce the number of LSAs exchanged.

The election of the DIS is based on the highest priority . If the priority is the same, the router with the highest System ID becomes the DIS.

The monitoring plane ' s primary role is environmental monitoring, ensuring the stability of the system. Functions like voltage monitoring, temperature tracking, fan speed control, and power management are standard. These are independent of the forwarding or control planes and critical for maintaining device health in network operations ​.

Comprehensive and Detailed Step-by-Step Explanation:

1. Single-Hop BFD Session:

A single-hop BFD session is used to detect link failures between directly connected devices.

It is bound to the local IP address and the peer IP address , and the session relies on these parameters to establish connectivity.

2. Why Modifications Require Deletion:

BFD sessions are tightly bound to their configuration parameters (e.g., local and peer IP addresses).

Modifying these parameters is not supported for an existing session. Instead, you must delete the session and recreate it with the updated parameters.

3. Why the Statement is TRUE:

The statement correctly describes the behavior of BFD sessions, where modifying an existing session is not possible without deleting it first.

This statement is false because IGMPv2 improves upon IGMPv1 by introducing the Leave Group message .

In IGMPv1 , members leave silently, and the router waits for the timeout.

In IGMPv2 , a host sends a Leave Group message, prompting the router to send a Group-Specific Query to determine if other members are still present. If no responses are received, the group is pruned before timeout.

Reference from Huawei HCIP-Datacom-Core Technology Study Guide:

“IGMPv2 allows group members to actively send Leave messages, reducing unnecessary forwarding delays. This improves efficiency over IGMPv1.”

(Chapter: Multicast Protocols – Section: IGMP Versions)

The MED (Multi-Exit Discriminator) is an optional, non-transitive attribute used to influence the exit path. MED is considered after attributes such as Local-Preference, AS-Path, and Origin during route selection. By default, if a MED value is missing, it is treated as 0 unless the bestroute med-none-as-maximum command is configured to treat it as 4294967295 ​.