H12-821_V1.0 Exam Dumps - HCIP-Datacom-Core Technology V1.0

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.

Comprehensive and Detailed In-Depth Explanation:

IPsec (IP Security Protocol)establishesSecurity Associations (SAs)for encrypted communication.

AnSA is uniquely identified by a 3-tuple:

SPI (Security Parameter Index)→ Identifies the SA.

Destination IP Address→ Specifies the receiving device.

Security Protocol ID→ Indicates whetherAH (Authentication Header) or ESP (Encapsulating Security Payload)is used.

A. Key exchange protocolisnotpart of theSA 3-tuple. It is used duringIKE (Internet Key Exchange)but is not part of the SA itself.

📖Reference:Huawei HCIA-Datacom Study Guide, IPsec Security Association and SA Identification.

The hardware modules of Huawei modular devices and their functions are:

Main Processing Unit (MPU):Provides control and management planes for the entire system, responsible for protocol processing, system security, and software upgrades.

Switch Fabric Unit (SFU):Provides the data plane, enabling high-speed data switching between service modules.

Line Processing Unit (LPU):Manages data forwarding, offering various interfaces (optical and electrical) for data access​​.

In asynchronous mode, two devices exchange BFD Control packets to monitor connectivity. However, this mode does support the echo function, which tests bidirectional paths by sending packets that loop back to the origin. This statement is incorrect. Demand mode, on the otherhand, minimizes the control packet exchange, relying on periodic echo packets if configured. Huawei's BFD configuration guides emphasize these distinctions ​.

According to BGP route selection rules, a higherLocal_Prefvalue indicates a more preferred route. This rule is used to influence traffic flow within an autonomous system (AS), giving preference to routes with a higherLocal_Preffor outgoing traffic ​.

Comprehensive and Detailed Step-by-Step Explanation:

Single-Hop BFD:

Single-hop BFD is used for detecting link failures in directly connected devices.

It usesUDP port 3784for communication.

Multi-Hop BFD:

For multi-hop scenarios, BFD usesUDP port 4784to ensure end-to-end connectivity.

Incorrect Options:

TCP ports 3784 and 4784 (C and D):BFD does not use TCP.

ï‚· VRRP and BFD Association:

VRRP (Virtual Router Redundancy Protocol) is used to provide gateway redundancy by electing amasterandbackuprouter.

Associating VRRP with BFD (Bidirectional Forwarding Detection) allows faster detection of faults on the master device or the link between the master and the backup.

HCIP-Datacom-Core Technology Training Material (VRRP and BFD Association)​.

ï‚· Master_Down_Timer Behavior:

Normally, when a VRRP backup device detects that the master is down (through missed VRRP advertisements), theMaster_Down_Timerdictates the failover timing.

However, when VRRP is associated with BFD:

BFD detects faults immediately (sub-second detection).

The backup device doesnot wait for the Master_Down_Timerto expire. Instead, it immediately assumes the master role upon fault detection by BFD.

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 ​.