Huawei H12-821_V1.0 - HCIP-Datacom-Core Technology V1.0

Comprehensive and Detailed Step-by-Step Explanation:

Overview of IGMP Versions:

IGMPv1:The simplest version, supports basic group membership management using Report messages but lacks Leave messages.

IGMPv2:Adds features like Leave messages and Group-Specific Queries.

IGMPv3:Supports specifying multicast sources for Source-Specific Multicast (SSM).

Feature Supported by All Versions:

Report messagesare fundamental to IGMP functionality and are supported in all three versions.

Features Not Supported by All Versions:

Group-Specific Queries (A):Supported in IGMPv2 and IGMPv3.

Leave Messages (B):Introduced in IGMPv2.

Specifying Multicast Sources (D):Introduced in IGMPv3.

Comprehensive and Detailed In-Depth Explanation:

A. TRUE→ Firewalls maintainsession tableswith adefault session timeout; adjusting it depends onnetwork conditions.

B. FALSE→Fast session aging does not affect persistent connection sessions. Persistent connections (e.g., TCP keepalives)maintain sessionseven if aging settings change.

C. TRUE→ Sessionsmust be constantly matchedwith ongoing traffic to remainactive.

D. TRUE→ Evenwithout stateful inspection, the firewallcreates session entriesfornon-first packetsto maintaincontinuity of services.

📖Reference:Huawei HCIA-Datacom Study Guide, Firewall Session Table Mechanism.

Comprehensive and Detailed Step-by-Step Explanation:

1. BGP Attributes Overview:

BGP uses attributes to describe the properties of routes. These attributes are classified into the following categories:

Well-Known Mandatory: Attributes that must be recognized and included in every BGP update. Examples: AS_PATH, ORIGIN, NEXT_HOP.

Well-Known Discretionary: Attributes that must be recognized but are not required in every BGP update. Examples: LOCAL_PREF, ATOMIC_AGGREGATE.

Optional Transitive: Attributes that may or may not be recognized, but must be passed along to other BGP peers. Examples: COMMUNITY.

Optional Non-Transitive: Attributes that may or may not be recognized, and are not passed along to other BGP peers. Examples: MED (Multi-Exit Discriminator).

2. Analysis of Each Option:

Option A: Atomic_Aggregate

Correct.

This is a well-known discretionary attribute. It indicates that the advertised route is an aggregate route that summarizes multiple specific routes.

Option B: Local-Preference

Correct.

This is a well-known discretionary attribute. It is used within an AS to prioritize routes, with higher values being preferred.

Option C: Community

Incorrect.

The COMMUNITY attribute is an optional transitive attribute. It is used to tag routes with specific labels to apply routing policies.

Option D: MED (Multi-Exit Discriminator)

Incorrect.

The MED attribute is an optional non-transitive attribute. It is used to influence the choice of the preferred path when there are multiple entry points into an AS.

3. Summary:

Well-Known Discretionary Attributes: Atomic_Aggregate and Local-Preference.

Huawei HCIA-Datacom Study Guide, Chapter "BGP Route Attributes."

RFC 4271: Border Gateway Protocol 4 (BGP-4).

Comprehensive and Detailed In-Depth Explanation:

BFD (Bidirectional Forwarding Detection)detectslink failuresfaster than traditional mechanisms.

Session states during setup:

AdminDown→ Initial state (session is administratively disabled).

Down→ The session is being established but has not yet exchanged valid control packets.

Init→ The session is partially established (one side has detected the peer).

Up→ The session is fully operational (not part of the setup process).

SinceAdminDown, Down, and Initare involved insession setup, the correct answers areB, C, D.

📖Reference:Huawei HCIA-Datacom Study Guide, BFD Session Establishment and States.

Comprehensive and Detailed In-Depth Explanation:

OSPF-to-BGP route redistributiondoesnot allow modification of MED valuesdirectly using aroute-policyin Huawei devices.

Instead,MED can be set using a BGP attribute policy, not through the import command.

All other options (B, C, D) are correct:

B→ Route-policycan filter imported direct routes.

C→ network commanddoes not modify attributes, only announces existing routes.

D→ peer commandcan set Local Preferencevia route-policy.

📖Reference:Huawei HCIA-Datacom Study Guide, BGP Route Policy and Attribute Modification.

Inasynchronousmode, the local device sends BFD control packets at predefined intervals, and the remote device monitors the receipt of these packets to detect connectivity issues. This is one of the two operating modes in BFD, the other beingdemandmode ​.

Comprehensive and Detailed In-Depth Explanation:

A. TRUE→ Ifpreemption is enabled, ahigher-priority routercan take over as theMaster.

B. TRUE→ Ifpreemption is disabled, thecurrent Master remains activeeven if a higher-priority router joins.

C. TRUE→ TheMaster router sends VRRP Advertisement packetsto maintain its role.

D. FALSE→ If aVRRP router is the IP address owner, itautomatically becomes the Masterwithout needing toparticipate in an election.

📖Reference:Huawei HCIA-Datacom Study Guide, VRRP Priority and Preemption Mechanisms.

Access Control Lists (ACLs) can be classified into several types, including Basic ACL (filters based on source IP), Advanced ACL (filters based on multiple parameters like source and destination IP, protocol, and ports), and Layer 2 ACL (filters based on MAC addresses). User-defined ACLs are not a standard classification ​.

To compress the IPv6 address 2001:0DB8:0000:C030:0000:0000:09A0, the following rules are applied:

Remove leading zeros in each hextet (e.g., 0DB8 becomes DB8).

Replace contiguous blocks of zeros with :: (only once in the address).Thus, the compressed form is 2001:DB8:0:C030::9A0 ​.

The correct command for configuring the VRRP (Virtual Router Redundancy Protocol) preemption delay isvrrp vrid 1 preempt-delay 20. This command sets the delay before a higher-priority VRRP router preempts the master role, ensuring stable operation during network transitions ​.