Huawei Updated H12-821_V1.0 Exam Questions and Answers by macy

Attributes such as community , tag , and origin can be directly referenced in the apply clause of a route-policy. However, IP-prefix is not an attribute but a prefix list used for matching, and it cannot be directly applied ​.

Comprehensive and Detailed Step-by-Step Explanation:

1. Understanding the IGMP Group Entry:

The IGMP group entry contains key information about multicast groups on the interface:

Group Address (225.1.1.2): The multicast group address that the user has joined.

Last Reporter (10.1.6.10): The IP address of the last host that sent an IGMP Report message for this group.

Uptime: The duration since the group was first reported.

Expires: The remaining time before the group entry ages out if no further reports are received.

2. Analysis of Each Statement:

Option A: This entry can be used to construct the corresponding (S, G) entry.

Incorrect.

This is a group entry for IGMP, which contains information about the group (G) but does not include a specific source (S). (S, G) entries are created in PIM (Protocol Independent Multicast), not IGMP.

Option B: This entry is created when the device receives an IGMP Join message from a user.

Correct.

IGMP Join messages are used by hosts to signal their intent to join a multicast group. When such a message is received, the group entry is created.

Option C: Expires indicates the aging time of the IGMP group.

Correct.

The " Expires " field shows the remaining time before the group entry ages out if no further IGMP reports are received.

Option D: 225.1.1.2 is the address of the group that the user joins.

Correct.

The " Group Address " field explicitly states that 225.1.1.2 is the multicast group that the user has joined.

3. Summary:

Correct Options: B, C, D

A is false – The correct formula is: Skew_Time = (256 - Priority)/256 × Advertisement_Interval.

B is false – By default, the preemption delay is typically 0s , not 1s, meaning a higher-priority backup router can preempt immediately unless configured otherwise.

C is true – The default Advertisement interval in VRRP is 2 seconds .

D is true – The formula Master_Down_Interval = 3 × Advertisement_Interval + Skew_Time is correct.

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

“The VRRP Skew_Time is calculated as (256 - Priority)/256 × Adver_Interval. The Master_Down interval includes this Skew_Time to stagger failover.”

(Chapter: High Availability – Section: VRRP Timer Mechanism)

 IP Prefix List Matching Conditions

An IP prefix list matches based on:

Mask : Specifies the subnet mask length.

Action : Specifies whether to permit or deny.

Index : Orders the rules within the prefix list.

Port numbers are not applicable as matching conditions in an IP prefix list.

 HCIP-Datacom-Core Reference

IP prefix list configurations are detailed in the routing policy and route filtering chapters​​.