H12-821_V1.0 Exam Dumps - Huawei HCIP-Datacom Questions and Answers

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Explanation of Root Port Election in STP:

In a Spanning Tree Protocol (STP) network, the Root Port is selected on each switch (except the Root Bridge). The Root Port is the port with the lowest path cost to the Root Bridge. If there is a tie in path cost, the following criteria are used in sequence to break the tie:

Steps for Root Port Election in Sequence:

RPC Comparison (Root Path Cost):

The port with the lowest Root Path Cost is preferred.

Root Path Cost is the cumulative cost of the path to the Root Bridge.

Peer BID (Bridge ID) Comparison:

If the Root Path Costs are equal, the Bridge ID of the connected switch (peer) is compared.

The port connecting to the switch with the lower Bridge ID is preferred.

Peer PID (Port ID) Comparison:

If the Bridge IDs are equal, the Port ID of the peer's sending port is compared.

The port connecting to the lower Port ID is preferred.

Local PID (Port ID) Comparison:

If all else is equal, the Local Port ID of the switch is used.

The port with the lower Local Port ID is selected.

The silent-interface command disables the sending of OSPF packets, including Hello packets, on the specified interface, which prevents the establishment of OSPF neighbor relationships. However, the interface can still advertise directly connected routes through other interfaces, making Option C incorrect ​.

 ACL Number Ranges

Basic ACLs: Numbered from 2000 to 2999.

Advanced ACLs: Numbered from 3000 to 3999.

Layer 2 ACLs: Numbered from 5000 to 5999.

User-defined ACLs: Numbered from 4000 to 4999.

 HCIP-Datacom-Core Reference

ACL classifications and their number ranges are covered in the ACL principles and configuration chapters​​.

In Layer 3 roaming scenarios, STAs (stations) remain on different subnets before and after roaming. To ensure that user traffic reaches the original subnet, it must be tunneled back over a CAPWAP tunnel. This technique prevents disruptions in communication and enables seamless roaming. Huawei’s Layer 3 roaming design guidelines emphasize the use of CAPWAP tunnels for user traffic forwarding ​.

Comprehensive and Detailed Step-by-Step Explanation:

Routing Table Structure:

Routers maintain a local core routing table and separate protocol routing tables for OSPF, BGP, etc.

The local core routing table stores optimal routes selected based on metrics, protocol preferences, and administrative distances.

Fields in the Core Routing Table:

Destination Address (A): Indicates the destination network or host.

Routing Protocol Preference (B): Determines the priority of routing protocols (e.g., OSPF > RIP).

Routing Protocol (D): Specifies the protocol (e.g., OSPF, BGP) that contributed the route.

Inbound Interface: This is stored in the protocol-specific routing table but not in the local core table.

References:

HCIA-Datacom Study Guide, Chapter: Routing Table Management

Huawei Routing Fundamentals

Comprehensive and Detailed in-depth Step-by-Step Explanation:To answer this question, it is essential to distinguish between the roles of ABRs and ASBRs in OSPF and the function of route summarization:

Route Summarization on ABRs:

Route summarization in OSPF can reduce the number of inter-area Type 3 LSAs that ABRs propagate between areas.

ABRs perform route summarization to reduce the amount of routing information exchanged between areas, thereby decreasing the size of the routing table and improving resource utilization.

Route Summarization on ASBRs:

ASBRs summarize external routes (from outside OSPF) into Type 5 LSAs or Type 7 LSAs (in NSSAs).

ASBR route summarization does not impact inter-area Type 3 LSAs because ASBRs are responsible for importing and summarizing external routes, not summarizing routes between OSPF areas.

Since the statement refers to configuring route summarization on ASBRs to reduce inter-area Type 3 LSAs, it is incorrect. Route summarization for inter-area Type 3 LSAs must be configured on ABRs, not ASBRs.

Correct Statement: Route summarization on ABRs reduces the number of inter-area Type 3 LSAs.

References:

Huawei HCIA-Datacom Study Guide, Chapter on "OSPF Route Summarization".

RFC 2328 – OSPF Version 2.

Comprehensive and Detailed in-depth Step-by-Step Explanation:OSPF routers establish neighbor relationships and progress through various states during the adjacency formation process. The ExStart state is where routers negotiate the master and slave roles. This negotiation is critical because the master initiates the Data Description (DD) packet exchange process.

Here’s a breakdown of the relevant OSPF states:

ExStart State:

This is the phase where the routers determine which one will act as the master and which will be the slave.

The decision is based on the Router IDs of the two routers. The router with the higher Router ID becomes the master.

Exchange State:

After the master-slave roles are established, the routers exchange DD packets. These packets contain summaries of the LSAs in their respective LSDBs.

2-way State:

This state indicates that bidirectional communication has been established between the two routers, but it occurs before master-slave negotiation.

Init State:

This is an early state where a router has sent a Hello packet to its neighbor but has not yet received a Hello packet in response.

Key Point:The negotiation of master and slave roles happens exclusively in the ExStart state, making D. ExStart the correct answer.

References:

Huawei HCIA-Datacom Study Guide, Chapter on "OSPF Neighbor States".

RFC 2328 – OSPF Version 2 (Section 10.8).

Comprehensive and Detailed Step-by-Step Explanation:

1. Understanding the Prefix List Configuration:

The command ip ip-prefix test index 10 permit 10.0.0.0 8 less-equal 32 defines the following:

The prefix base is 10.0.0.0 with a mask length of 8 bits.

The less-equal 32 condition allows routes with mask lengths ranging from 8 to 32 bits to match.

2. Analysis of Each Route:

Option A: 10.1.1.1/32

Correct.

The prefix 10.1.1.1/32 falls within the 10.0.0.0/8 network range and has a mask length of 32 bits, which satisfies the less-equal 32 condition.

Option B: 10.1.1.0/6

Incorrect.

The prefix 10.1.1.0/6 has a mask length of 6 bits, which is shorter than the base prefix length of 8. It does not satisfy the condition.

Option C: 10.1.1.0/24

Correct.

The prefix 10.1.1.0/24 falls within the 10.0.0.0/8 network range and has a mask length of 24 bits, which satisfies the less-equal 32 condition.

Option D: 10.0.0.0/16

Correct.

The prefix 10.0.0.0/16 falls within the 10.0.0.0/8 network range and has a mask length of 16 bits, which satisfies the less-equal 32 condition.

3. Summary:

The prefixes that match the configuration are 10.1.1.1/32, 10.1.1.0/24, and 10.0.0.0/16.

 Understanding Router ID and Its Role in OSPF:In OSPF, the Router ID uniquely identifies a router within the OSPF domain. If two routers are configured with the same Router ID, it can lead to issues such as LSA conflicts and flapping. This is because the Router ID is used as a key in OSPF operations, including LSA generation and database synchronization.