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

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 a3-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.

TheLS Sequence Numberis 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.

Comprehensive and Detailed Step-by-Step Explanation:

1. Features of Wi-Fi 6:

Wi-Fi 6 (802.11ax) introduces several new technologies to improve network efficiency, reduce latency, and optimize power usage:

OFDMA (Orthogonal Frequency Division Multiple Access):Allows multiple devices to transmit simultaneously, improving concurrency.

TWT (Target Wake Time):Reduces power consumption by scheduling communication times for devices.

High Bandwidth:Supports up to 9.6 Gbps, significantly faster than Wi-Fi 5.

2. Why Zero Latency is Incorrect:

While Wi-Fi 6 reduces latency compared to earlier standards,zero latencyis not achievable due to inherent delays in network communication.

The statement "Realizes zero latency" is misleading and technically inaccurate.

3. Analysis of Each Option:

Option A: Uses OFDMA technology to achieve high concurrency.

Correct (True Statement).

OFDMA is a core feature of Wi-Fi 6 that improves concurrent communication.

Option B: Realizes zero latency, ensuring efficient service running.

Incorrect (False Statement).

Wi-Fi 6 reduces latency but cannot eliminate it entirely.

Option C: Provides high bandwidth, up to 9.6 Gbps.

Correct (True Statement).

Wi-Fi 6 supports a theoretical maximum bandwidth of 9.6 Gbps.

Option D: Uses TWT technology to reduce terminal power consumption.

Correct (True Statement).

TWT schedules communication times, allowing devices to enter low-power states and conserve battery life.

4. Summary:

Thefalsestatement isB, as Wi-Fi 6 does not achieve zero latency.

In OSPF (Open Shortest Path First), each router maintains aLink-State Database (LSDB), which must be synchronized with other routers in the same area. When an OSPF router receives anLSA (Link-State Advertisement)that it doesnot already have in its LSDB, it takes the following steps:

It updates its LSDB with the new LSA.

It floods the LSA to all its other OSPF neighbors (except the one from which it received the LSA).

This ensures that all routers in the OSPF area eventually converge to the same network topology.

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

“When an LSA is received and it is newer or not present in the LSDB, the router updates the LSDB and floods the LSA to other neighbors to ensure database synchronization.”

(Chapter: OSPF Fundamentals – Section: LSDB Synchronization)

Thedefault Hello intervalon an OSPF P2P (Point-to-Point) or Broadcast network is10 seconds, and thedefault Dead intervalis40 seconds.

The Dead interval is the time a router waits without receiving a Hello packet from a neighbor before declaring it down.

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

“For broadcast and P2P network types, the default Hello interval is 10 seconds and the Dead interval is 40 seconds.”

(Chapter: OSPF Interface Types – Section: OSPF Timers)

Configuration Analysis:

OnR2, the following configuration has been applied:

acl 200

rule deny source 10.1.0.0 0.0.3.0

rule permit

#

ospf 1

filter-policy 2000 import

This configuration usesACL 200to filter routes during import into the OSPF routing table on R2.

Rule deny source 10.1.0.0 0.0.3.0:Blocks routes in the range10.1.0.0/24 to 10.1.3.0/24(inclusive).

Rule permit:Allows all other routes to be imported.

Impact of ACL 200 on Route Import:

10.1.0.0/24 to 10.1.3.0/24:These subnets are explicitly denied by ACL 200 and will not appear in R2's routing table.

10.1.4.0/24 and beyond:These subnets are permitted by therule permitstatement and will be imported into R2's routing table.

Routing Table Entries on R2:

Option A (10.1.4.0/24):Exists in R2's routing table because it is permitted.

Option B (10.1.3.0/24):Does not exist because it is denied by ACL 200.

Option C (10.1.2.0/24):Does not exist because it is denied by ACL 200.

Option D (10.1.1.0/24):Does not exist because it is denied by ACL 200.

A (10.1.4.0/24)

Comprehensive and Detailed In-Depth Explanation:

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

NBMA (Non-Broadcast Multi-Access)networks (e.g., Frame Relay) donot support multicast, so routers mustunicastOSPF packets to neighbors.

Broadcast networks(e.g., Ethernet) supportmulticastand use224.0.0.5 for Hello packetsand224.0.0.6 for DR/BDR communication.

The statement isfalsebecause:

NBMA does not unicast all packets—only Hello packets must bemanually configuredto be unicast.

LSAs and routing updates can still be multicastif an NBMA network is configured aspoint-to-multipoint.

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

Comprehensive and Detailed In-Depth Explanation:

BGP does not support automatic summarization for IPv6 networks.

InIPv4, BGP could performautomatic summarizationatclassful boundaries, but this feature isnot supported for IPv6.

Manual summarizationcan be configured usingaggregate IPv6 addresses(e.g., using the aggregate-address command).

Since the statement incorrectly claims thatBGP supports automatic summarization for IPv6, it isfalse.

📖Reference:Huawei HCIA-Datacom Study Guide, BGP Route Summarization for IPv4 and IPv6.

The mandatory parameters for BGP peer configuration are the peer IP address (peer ip-address) and AS number (as-number). A password is optional for MD5 authentication, and a description is an optional comment for reference. These are not required for establishing the peer relationship ​.

Comprehensive and Detailed In-Depth Explanation:

AS_Pathis awell-known mandatoryattribute (not discretionary).

AS_Path characteristics:

A. TRUE→When advertising to IBGP peers, AS_Path remains unchangedto prevent routing loops.

B. TRUE→BGP uses AS_Path to detect loops(if a router sees its own AS in the path, it rejects the route).

C. FALSE→ AS_Path iswell-known mandatory, not discretionary.

D. TRUE→BGP ignores AS_Confed_Sequence and AS_Confed_Setwhen calculating the AS_Path length.

📖Reference:Huawei HCIA-Datacom Study Guide, BGP Path Attributes and Loop Prevention.

ï‚· DIS and DR Election

The IS-IS Designated Intermediate System (DIS) is responsible for generating and updating pseudonode LSPs on a broadcast network.

Unlike OSPF DR, the IS-IS DIS does not preempt by default. This behavior avoids unnecessary flapping in the network due to frequent DIS re-elections.

ï‚· HCIP-Datacom-Core Reference

The characteristics of DIS and DR behavior are explained in IS-IS network operation chapters​​.