Comprehensive and Detailed Step-by-Step Explanation:

1. What is First-Time Authentication in SSH?

When an SSH client connects to an SSH server for the first time, the server's public key is not yet known to the client.

Enabling first-time authentication allows the SSH client to accept the server's public key and save it for future connections. This feature eliminates the need for manual configuration of the server's public key on the client.

2. Process Explanation:

The SSH client connects to the server and receives the server's public key.

The client accepts the key and saves it in its local key database (e.g., known_hosts file).

For subsequent connections, the client uses the saved public key to authenticate the server.

3. Why the Statement is TRUE:

First-time authentication simplifies SSH setup and is a commonly used method when connecting to new servers. It ensures that future connections are authenticated using the saved public key.

The native AC (Access Controller) function in Huawei's agile switches enables wired and wireless convergence. This integration allows the agile switch to act as both a wired network switch and a wireless controller, managing all traffic centrally. This architecture simplifies network management and improves efficiency, making the statement true ​.

In an OSPF broadcast or NBMA network with at least two routers, one router must act as the DR (Designated Router), and another as the BDR (Backup Designated Router) to ensure efficient communication and reduce the number of adjacencies. This is a requirement for OSPF operation in such network types ​.

Comprehensive and Detailed Step-by-Step Explanation:

1. Understanding the AS-Path Filter:

The as-path-filter command is used in BGP to filter routes based on the AS_PATH attribute.

In this configuration:

The filter si is defined with the regular expression _65500$.

The _65500$ expression specifies that the AS_PATH must end with 65500, meaning that the route's last hop must have passed through AS 65500.

2. Option Analysis:

Option A: It accepts only the routes whose AS_Path contains AS 65500.

Incorrect.

The _65500$ filter specifically matches routes where AS 65500 is the last AS in the AS_PATH. A route may contain AS 65500 somewhere in the middle of the AS_PATH but will not match this filter unless it is the last AS.

Option B: It accepts only the routes originated from AS 65500.

Incorrect.

Routes that originate from AS 65500 have an AS_PATH that starts with 65500. However, the filter _65500$ only matches routes where AS 65500 is the last AS, not the first AS.

Option C: It accepts only the routes that last pass through AS 65500.

Correct.

The _65500$ filter ensures that the AS_PATH ends with 65500. This means that the route must have last passed through AS 65500 before being received by the local BGP router.

Option D: It accepts only the routes forwarded by AS 65500.

Incorrect.

While AS 65500 may forward the route, this is not what the filter _65500$ specifically checks for. It only ensures that AS 65500 is the last AS in the AS_PATH.

3. Summary:

The as-path-filter with _65500$ accepts only the routes where AS 65500 is the last AS in the AS_PATH.

Comprehensive and Detailed Step-by-Step Explanation:

IS-IS Area Division:

IS-IS divides areas by routers, not by links. A router is assigned to a specific IS-IS area, but it can belong to multiple levels:

Level 1: Maintains the LSDB (Link State Database) for the local area only.

Level 2: Maintains the LSDB for the backbone area and exchanges routes between areas.

Behavior of a Level 1-2 Router:

A router configured as Level 1-2 must maintain two separate LSDBs:

One for intra-area routes (Level 1).

One for inter-area routes (Level 2).

Incorrect Statement:

The statement that an IS-IS router only needs to maintain the LSDB of its area is incorrect because Level 1-2 routers maintain LSDBs for both levels.

References:

HCIA-Datacom Study Guide, Chapter: IS-IS Area Structure

Huawei IS-IS Fundamentals

In BGP, the AS-Path attribute is mandatory and must be included in all UPDATE messages. It records the autonomous systems a route has traversed. Attributes like Local-Preference, MED, and Prefval are optional and may not always be included. The AS-Path is crucial for loop prevention and route selection ​.

 ACL Matching in Huawei Routers:

Access Control Lists (ACLs) are used to filter packets based on specific criteria, such as source/destination IP, ports, or protocols.

When a packet arrives, the Huawei router processes it against the configured ACL rules to decide whether to permit or deny the packet.

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.

The virtual MAC address for a VRRP virtual router is determined by the formula 00-00-5E-00-01-[VRID in hexadecimal]. For VRID 3, the hexadecimal equivalent is 03. Thus, the virtual MAC address is 00-00-5E-00-01-03 ​.

ARP spoofing is a Layer 2 attack, as it targets ARP tables in switches or end devices. All other attacks, including IP spoofing, ICMP attacks, and Smurf attacks, are network layer (Layer 3) attacks ​.

BFD operates at the network layer, providing rapid fault detection for forwarding paths, such as IP routing and MPLS tunnels. It interacts closely with network protocols (e.g., OSPF, BGP) to ensure high reliability and quick response to faults. BFD does not belong to the application, data link, or physical layers but functions as a network layer diagnostic tool as confirmed in Huawei's network protocol training ​.

By default, Huawei firewalls create security zones named untrust, dmz, trust, and local. These zones facilitate security policies for inbound, outbound, and inter-zone traffic control ​.

In OSPF, DR and BDR listen on the multicast address 224.0.0.6, while all OSPF routers (including DR others) listen on 224.0.0.5. DR others establish neighbor relationships with DR and BDR, but they do not listen on 224.0.0.6. This makes Option D incorrect, as only DR and BDR use 224.0.0.6 ​.

The preference of routing protocols determines the selection order of routes when a router receives multiple routes to the same destination from different routing protocols. For instance, OSPF has a higher preference over RIP, so OSPF routes will be selected first. Huawei routing preferences confirm this behavior ​.

The command output indicates that the OSPF neighbor state is Full and that the neighbor relationship has been established. The statement confirms that the negotiation process during the exchange of DD (Database Description) packets has determined the role of the router, with the local device becoming the slave in the Master-Slave relationship, which is critical for LSA synchronization. The other options do not align with the output or OSPF principles ​

When STP and RSTP coexist in a network, RSTP switches will downgrade their operation to STP to ensure compatibility. However, this disables RSTP's rapid convergence features, as the protocol behaves like STP to maintain interoperability ​.

Comprehensive and Detailed Step-by-Step Explanation:

Single-Hop BFD:

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

It uses UDP port 3784 for communication.

Multi-Hop BFD:

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

Incorrect Options:

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

References:

HCIA-Datacom Study Guide, Chapter: BFD Ports and Functions

Huawei BFD Configuration Details

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 ​.

 OSPF LSA Flooding Mechanism

If a router receives an LSA identical to one already in its LSDB, it does not flood the LSA again unless the LSA has changed (i.e., the sequence number or content has been updated).

OSPF ensures efficient use of bandwidth by avoiding redundant flooding of unchanged LSAs.

 HCIP-Datacom-Core Reference

The OSPF LSDB synchronization process explains that unchanged LSAs are not reflooded, ensuring stability and resource optimization​​.

 Notification Message Purpose

BGP Notification messages are used to report errors or terminate a connection. They do not request peers to resend routing information after routing policies are changed.

Routing updates following policy changes require manual resynchronization, not Notification messages.

 HCIP-Datacom-Core Reference

The purpose and usage of Notification messages are discussed in the BGP operation chapters​​.

When configuring VRRP, the virtual router priority and virtual IP address are mandatory because they define the VRRP instance and its role within the group. Preemption mode and preemption delay are optional configurations that influence how routers take over the master role when priorities change. These are not mandatory for the VRRP protocol to function ​.

Comprehensive and Detailed in-depth Step-by-Step Explanation:In an Intermediate System to Intermediate System (IS-IS) network, a Designated Intermediate System (DIS) is elected on broadcast networks to perform the following functions:

Represent the broadcast network as a pseudonode.

Generate and update the Link State Protocol Data Units (LSPs) for the pseudonode.

The DIS is elected based on the DIS priority value, which is configured on IS-IS interfaces. If two routers have the same priority, the router with the higher MAC address becomes the DIS.

The default DIS priority for IS-IS interfaces is 64, which can be modified depending on the network requirements.

Option A (200): Incorrect. This is not the default value.

Option B (64): Correct. This is the default DIS priority value.

Option C (1): Incorrect. This is not the default value.

Option D (100): Incorrect. This is not the default value.

References:

Huawei HCIA-Datacom Study Guide, Chapter on "IS-IS Basics".

RFC 1195 – Use of OSI IS-IS for Routing in TCP/IP and Dual Environments.

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 messages are 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.

References:

HCIA-Datacom Study Guide, Chapter: IGMP Overview

Huawei Multicast Protocol Details

In PIM-DM (Protocol Independent Multicast - Dense Mode), the SPT (Shortest Path Tree) establishment process involves flooding to propagate multicast traffic across the network, prune messages to stop sending multicast traffic to unwanted interfaces, and graft messages to re-establish forwarding when needed. State-refresh is not directly involved in SPT establishment but helps maintain the prune state ​.

Inter-area route calculation in OSPF involves Summary LSAs (Type 3) for summarizing routes across areas and ASBR Summary LSAs (Type 4) for locating ASBRs. While Router LSAs and Network LSAs describe the internal structure of an area, they do not directly participate in inter-area route calculation. Thus, the statement that only Router, Network, and Summary LSAs are involved is false ​.

Understanding DIS Election in IS-IS:

On an IS-IS broadcast network, a Designated Intermediate System (DIS) is elected to create and update pseudonodes for efficient communication.

The election is based on the following criteria:

DIS Priority: The router with the highest priority is elected as the DIS.

Router ID (tie-breaker): If priorities are equal, the router with the highest Router ID is elected.

Analyzing the DIS Priorities and Router IDs:

R1: Priority = 64, Router ID = 1.1.1.1

R2: Priority = 1, Router ID = 2.2.2.2

R3: Priority = 127, Router ID = 3.3.3.3

R4: Priority = 10, Router ID = 4.4.4.4

Among the routers, R3 has the highest DIS priority (127), making it the DIS.

Correct Option:

Option B (R3): Correct, as R3 has the highest priority.

Option A (R1): Incorrect, as its priority is lower (64).

Option C (R4): Incorrect, as its priority is lower (10).

Option D (R2): Incorrect, as its priority is the lowest (1).

References:

HCIA-Datacom Study Guide, Chapter: IS-IS DIS Election

Huawei IS-IS Configuration and DIS Role Details

The IPv6 address 2001:0DBB:B8:0000:C030:0000:0000:09A0:CDEF can be compressed by removing leading zeros in each segment and collapsing consecutive zero groups into ::. The result is 2001:DBB:B8:0:C030::9A0:CDEF ​.

When two BGP peers negotiate the Hold Time, the shorter value between the two configured Hold Time values is selected. This ensures compatibility and maintains the stability of the BGP session ​.

A screenshot of a computer Description automatically generated

Explanation of IS-IS Packet Types and Synchronization Process:

In the given scenario, R2 requests LSPs from R1 to synchronize its Link State Database (LSDB). The following IS-IS packet types are involved in this synchronization process:

1. P2P IIH (Point-to-Point IS-IS Hello):

Purpose: Establishes and maintains IS-IS neighbor relationships.

Step: This packet is exchanged initially to detect and maintain the adjacency between R1 and R2.

2. PSNP (Partial Sequence Number PDU):

Purpose: Requests missing or outdated LSPs (Link State PDUs) from a neighbor to synchronize the LSDB.

Step: In this case, R2 sends a PSNP to R1 to request the missing or outdated LSP.

3. LSP (Link State PDU):

Purpose: Contains routing information and is used to update the LSDB.

Step: R1 sends the requested LSPs to R2 for synchronization.

4. CSNP (Complete Sequence Number PDU):

Purpose: Lists all LSPs in the sender's LSDB to help neighbors verify and request missing LSPs.

Step: R1 sends a CSNP during retransmission timeout to notify R2 of its LSPs.

Comprehensive and Detailed Step-by-Step Explanation:

Portal Authentication:

Portal authentication uses a web-based mechanism where clients are redirected to a login page.

Communication between the access device and Portal server uses HTTP or HTTPS protocols.

Correct Statements:

Option A: HTTP or HTTPS is used for Portal authentication.

Option D: Portal protocol packets are transmitted over TCP for reliable communication.

Incorrect Statements:

Option B: Port 2000 is not the default for processing Portal packets.

Option C: The default destination port for communication with the Portal server is not 50100.

References:

HCIA-Datacom Study Guide, Chapter: WLAN Portal Authentication

Huawei WLAN Authentication Protocols

In dual-link MSB networking with load balancing, the new AP will connect to the AC with the lower number of connected APs. In this case, AC2 has only 20 connected APs, while AC1 has 100. Therefore, the new AP will connect to AC2 ​.

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 ​.

Comprehensive and Detailed Step-by-Step Explanation:

STP and RSTP Behavior:

STP: Only the designated port processes inferior BPDUs. Inferior BPDUs are received from downstream switches and typically indicate topology changes.

RSTP: All ports, regardless of role (root, designated, or alternate), process inferior BPDUs to ensure faster convergence.

Behavior Difference:

RSTP improves convergence by allowing any port to process inferior BPDUs, unlike STP, which restricts this function to designated ports.

References:

HCIA-Datacom Study Guide, Chapter: STP vs RSTP

Huawei STP and RSTP Configuration Comparison

Comprehensive and Detailed Step-by-Step Explanation:

1. Port Priority in RSTP:

RSTP (Rapid Spanning Tree Protocol) elects root and designated ports based on port priority and port ID.

Port priority is a configurable value that helps determine which port becomes the root or designated port when multiple ports are eligible.

The port ID consists of the port priority and port number. When priorities are equal, the port number is used as a tiebreaker.

2. Default Port Priority on Huawei Switches:

On Huawei switches, the default port priority is 128.

This value can be adjusted in increments of 16 using the command stp port priority.

3. Analysis of Options:

Option A: 1

Incorrect. This is not the default port priority value.

Option B: 128

Correct. This is the default port priority value on Huawei switches.

Option C: 4096

Incorrect. This is not a valid default port priority value.

Option D: 32768

Incorrect. This is the default bridge priority, not the port priority.

4. Summary:

The default port priority on Huawei switches is 128.

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

Multi-channel protocols such as H.323 and FTP use separate control and data channels. H.323 uses different channels for call signaling and media streaming, while FTP uses a control channel for commands and a data channel for file transfers. Telnet and SMTP are single-channel protocols ​.

GRE (Generic Routing Encapsulation) is not a Layer 2 VPN technology. Instead, it is a Layer 3 tunneling protocol used to encapsulate a wide variety of network layer protocols inside point-to-point connections. GRE is commonly used for creating VPN tunnels across IP networks, allowing for the transport of various types of payloads. This misunderstanding about GRE being a Layer 2 technology contradicts its definition and typical application ​.

Comprehensive and Detailed Step-by-Step Explanation:

iMaster NCE-Campus Overview:

iMaster NCE-Campus is Huawei’s network management platform for managing and controlling campus networks.

It supports user authentication, including STA (Station) authentication, in WLAN environments.

Authentication Modes Supported:

iMaster NCE-Campus integrates with AAA (RADIUS) servers to perform authentication for wireless clients.

Correct Statement:

The platform can function as an authentication server for WLAN STAs.

References:

HCIA-Datacom Study Guide, Chapter: WLAN Management with iMaster NCE-Campus

Huawei iMaster NCE-Campus Product Overview

Comprehensive and Detailed in-depth Step-by-Step Explanation:To establish an OSPF neighbor relationship, the following conditions must be met:

The routers must share a common network segment.

Their Hello and Dead intervals must match.

Their OSPF network types must be compatible.

The IP subnet masks must match.

If two OSPF routers are on different network segments and have different subnet masks, one solution is to change the OSPF network type to Point-to-Point (P2P) on both interfaces.

Point-to-Point (P2P):

In a P2P network type, OSPF ignores the subnet mask mismatch and establishes the neighbor relationship regardless of the network mask.

This is ideal for directly connected links between two routers.

NBMA (Non-Broadcast Multi-Access):

This network type is used for networks like Frame Relay or ATM, where a single physical interface connects to multiple neighbors.

It is not applicable to solving subnet mask mismatches for a single link.

P2MP (Point-to-Multipoint):

This type treats the link as multiple P2P links. It is mainly used in hub-and-spoke topologies.

While it can be configured to solve subnet mask mismatches, it is more complex and less commonly used compared to the P2P type.

Broadcast:

This type requires all routers on the same segment to agree on subnet masks, so it cannot resolve the subnet mask mismatch issue.

Therefore, the correct answer is A. Point-to-point.

References:

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

RFC 2328 – OSPF Version 2, Section 10.

OSPF routers refresh and flood LSAs in the Link-State Database (LSDB) every 30 minutes by default to maintain topology consistency. OSPF does not rely on TCP; it uses its own acknowledgment mechanism. It also uses the Dijkstra algorithm, not Bellman-Ford. The flooding interval for LSU packets is shorter, typically 5 seconds ​.

1. Understanding Prefix List Configuration:

The command ip ip-prefix huawei index 10 permit 10.1.1.0 24 greater-equal 26 defines a prefix filter:

The base prefix is 10.1.1.0/24.

The greater-equal 26 condition specifies that the mask length of matching prefixes must be at least 26 bits.

If the less-equal parameter is not explicitly defined, the default value is 32, meaning the longest possible mask length for IPv4.

2. Explanation of Values:

greater-equal-value: Specifies the minimum mask length. In this case, the value is 26.

less-equal-value: Specifies the maximum mask length. Since it is not explicitly configured, the default value is 32.

3. Summary:

greater-equal-value = 26

less-equal-value = 32

One multicast MAC address maps to 32 multicast IP addresses due to the limited number of bits used in the mapping process. Specifically, the lower 23 bits of the MAC address map to the lower 23 bits of the multicast IP address, while the high 24 bits of the MAC address are fixed as 0x01005E. Thus, Option B is false ​.

Network Types and Corresponding Link Layer Protocols

Broadcast: Ethernet

Point-to-Point (P2P): PPP, HDLC

Point-to-Multipoint (P2MP): PPP

Non-Broadcast Multi-Access (NBMA): Frame Relay

 OSPF Network Types:OSPF classifies networks based on link layer protocols into the following types:

Broadcast: This type assumes that all routers on the network can communicate directly with one another using multicast or broadcast frames. Ethernet networks are typical examples.

Point-to-Point (P2P): This type is used for links that connect two routers directly. Common protocols include PPP (Point-to-Point Protocol) and HDLC.

Point-to-Multipoint (P2MP): This type simulates multiple point-to-point connections over a single physical network, often used in WAN scenarios where PPP is employed.

Non-Broadcast Multi-Access (NBMA): These networks connect multiple devices but lack native broadcast capability, such as Frame Relay.

High-availability Stateful Backup (HSB) ensures synchronization between active and standby devices. If the HSB channel fails to establish, the following causes are possible:

TCP channel not established: The HSB channel relies on a TCP connection. If the TCP session cannot be established, the backup process cannot start.

Mismatched retransmission settings: If the retransmission count and interval for HSB service packets are inconsistent between the two devices, the synchronization process fails.

Incorrect source and destination configurations: If the source IP address and port number on one device do not match the destination IP address and port number on the other, the channel cannot be established.

Option C is incorrect because the priority of the two ACs affects active/standby roles but does not directly impact HSB channel establishment ​.

Comprehensive and Detailed Step-by-Step Explanation:

1. What is L2TP (Layer 2 Tunneling Protocol)?

L2TP is a tunneling protocol used to transport Layer 2 frames over IP networks.

It is commonly used to establish VPNs but does not provide built-in encryption or security for the transmitted data.

2. Why L2TP Requires Additional Security Measures:

Since L2TP does not encrypt traffic, it is vulnerable to eavesdropping and tampering.

To secure L2TP tunnels, it is often paired with IPsec, which provides strong encryption and authentication. The combination of L2TP and IPsec is known as L2TP/IPsec.

3. Why the Statement is TRUE:

The statement accurately describes the limitation of L2TP (lack of encryption) and the need for additional security measures like IPsec.

 OSPF Authentication Overview

The Auth Type field in the OSPF packet header determines the authentication mode. If the Auth Type is 1, plaintext authentication is used.

Plaintext authentication involves transmitting the password in an easily readable format, which is less secure compared to MD5.

 HCIP-Datacom-Core Reference

Authentication mechanisms, including plaintext authentication, are detailed in the OSPF security configuration chapter, confirming that Auth Type = 1 corresponds to plaintext​​.

Comprehensive and Detailed Step-by-Step Explanation:

OSPF State Machine:

OSPF adjacency progresses through several states: Down > Init > 2-Way > ExStart > Exchange > Loading > Full.

The 2-Way state indicates that routers have exchanged Hello packets but are not forming full adjacencies.

Possible Causes for Staying in the 2-Way State:

Hello Time Values Are Different (A): Mismatched Hello/Dead intervals prevent adjacency establishment.

Area IDs Are Different (B): OSPF routers must belong to the same area to establish adjacency.

Router IDs Conflict (C): While Router ID conflicts cause other issues, they do not result in the 2-Way state.

N-bit and E-bit Are the Same (D): Matching N-bit/E-bit values are normal and do not cause problems.

References:

HCIA-Datacom Study Guide, Chapter: OSPF Adjacency Establishment

Huawei OSPF Neighbor State Analysis

Comprehensive and Detailed in-depth Step-by-Step Explanation:To answer this question, we need to understand the roles of OSPF routers:

Area Border Router (ABR):

An ABR is a router that connects multiple OSPF areas. It has at least one interface in the backbone area (Area 0) and one or more interfaces in other OSPF areas.

The ABR performs summarization between areas and propagates routing information between them.

Backup Router (BR):

The term "BR" does not exist in OSPF terminology. Instead, OSPF uses the term "Backup Designated Router (BDR)." The BDR is a backup to the Designated Router (DR) in a specific OSPF broadcast or NBMA (Non-Broadcast Multi-Access) network. The BDR takes over the DR's responsibilities if the DR fails.

Key Clarification:

An ABR is related to the hierarchical structure of OSPF areas and is not tied to the DR/BDR election process.

A router can function as an ABR without ever being a DR or BDR, as these are separate roles.

Therefore, the statement that an ABR must also be a BR is FALSE.

References:

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

RFC 2328 – OSPF Version 2.

Huawei OSPF Configuration Guide.

Configuration Analysis:

On R2, 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 uses ACL 200 to 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 range 10.1.0.0/24 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 the rule permit statement 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)

Correct Options:References:

HCIA-Datacom Study Guide, Chapter: OSPF Route Filtering

Huawei ACL Configuration for Route Policies

 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.

 During WLAN roaming, the STA sends a Reassociation Request frame to the foreign AP to maintain connectivity. Association frames are used during initial connections, not roaming.

 APs with which a STA is associated before and after roaming can work on different channels, as roaming often occurs across channels in environments like multi-SSID or multi-channel setups.Options C and D are false, as they contradict standard WLAN roaming procedures ​.

 IS-IS Overview: Intermediate System to Intermediate System (IS-IS) is a link-state routing protocol. Routers exchange Link State Packets (LSPs) to maintain a synchronized link-state database. These LSPs are categorized into Level-1 LSPs (intra-area routing) and Level-2 LSPs (inter-area routing). Both types share the same packet format.

BFD control packets are encapsulated in UDP packets, and the destination port number for multi-hop BFD control packets is 4784. This is a standardized port for multi-hop BFD operation ​.

 Permanent Group Addresses for Routing Protocols

The range 224.0.0.0 to 224.0.0.255 is reserved for local network protocols, including routing protocols. Examples include OSPF (224.0.0.5/6) and RIP (224.0.0.9).

 HCIP-Datacom-Core Reference

Reserved multicast address ranges are detailed in the multicast configuration sections​​.

 BGP Route Flapping and Mitigation

While route flapping is a concern in large-scale networks, BGP employs mechanisms such as Route Dampening to mitigate its impact. Route dampening suppresses frequently flapping routes for a period of time to reduce resource consumption and network instability.

Therefore, it is incorrect to state that the issue cannot be resolved in BGP.

 HCIP-Datacom-Core Reference

The mechanism of route dampening is detailed in the BGP optimization chapters​​.

Comprehensive and Detailed Step-by-Step Explanation:

OSPF Route Summarization:

Route summarization combines multiple specific routes into a single summary route. This reduces the number of LSAs advertised between OSPF areas, especially Type 3 LSAs.

Benefits of Route Summarization:

Reduces the size of the OSPF database and routing table.

Minimizes the processing overhead on routers by decreasing the number of routing entries.

Improves the scalability of the OSPF network.

ASBR Function:

The ASBR advertises external routes into OSPF and can summarize routes at area boundaries or during redistribution.

References:

HCIA-Datacom Study Guide, Chapter: OSPF Route Summarization

Huawei Routing Protocol Optimization

Comprehensive and Detailed Step-by-Step Explanation:

1. Overview of BGP:

BGP (Border Gateway Protocol) is an Exterior Gateway Protocol (EGP) designed to exchange routing information between different Autonomous Systems (ASs) on the internet. Unlike traditional distance-vector protocols (like RIP), BGP is considered a path-vector protocol, as it not only determines reachability but also ensures policy-based routing decisions and advanced path selection mechanisms.

2. Analysis of Each Option:

Option A: BGP does not support authentication. Therefore, it cannot ensure network security.

This statement is incorrect.

BGP supports authentication using mechanisms such as TCP MD5 (Message Digest 5) and TCP-AO (Authentication Option). These authentication mechanisms ensure that BGP messages are not tampered with or intercepted during transmission, enhancing network security.

Routing Entries in PIM

(S, G) entries: Represent the shortest path tree (SPT) from a specific source (S) to a specific multicast group (G). These entries are created after data packets are transmitted directly from the source to the receivers.

(S, G) entries are used in both PIM-DM and PIM-SM modes.

PIM-DM and PIM-SM Modes

In PIM-DM, multicast traffic is initially flooded throughout the network and pruned where no receivers exist. (S, G) entries represent source-specific paths created after the flooding stage.

In PIM-SM, multicast traffic initially flows through a shared tree, but (S, G) entries are created when the network switches to the SPT for more efficient forwarding.

HCIP-Datacom-Core Reference

The functionality and application of (S, G) routing entries are detailed in multicast and PIM configuration chapters​​.

OSPF process IDs are locally significant and do not need to match between routers to form neighbor relationships. The other statements correctly describe the behavior of OSPF multi-instances, making Option C false ​.

 ACL Modification

Named ACLs can be modified after their creation. Unlike numbered ACLs, named ACLs provide greater flexibility for editing individual rules without deleting the entire ACL.

Therefore, the statement is incorrect.

 HCIP-Datacom-Core Reference

The flexibility and editability of named ACLs are discussed in the ACL configuration sections​​.

In the provided configuration, IS-IS is enabled on Loopback0 but not on Loopback3 of R2. As a result, R2 will advertise the route 10.0.2.2/32 (from Loopback0) to R1 through IS-IS. However, the route 10.0.2.3/32 will not be advertised because IS-IS is not enabled on that loopback interface. The import-route direct command does not override this behavior ​.

Comprehensive and Detailed Step-by-Step Explanation:

OSPF Route Preference Hierarchy:

OSPF uses the following preference order for route types when the prefix is the same:

Intra-area routes (D): Routes within the same OSPF area have the highest priority.

Inter-area routes (B): Routes between different OSPF areas are preferred after intra-area routes.

Type 1 external routes (A): External routes redistributed into OSPF, considering the internal OSPF cost to the ASBR.

Type 2 external routes (C): External routes redistributed into OSPF, ignoring the internal OSPF cost to the ASBR.

Lowest Priority:

Type 2 external routes (C) are given the lowest priority because they represent external information that does not consider internal OSPF costs.

References:

HCIA-Datacom Study Guide, Chapter: OSPF Route Preference

Huawei OSPF Routing Table Selection Rules

 OSPF Area Design and Loop Prevention:OSPF uses a hierarchical structure with areas to improve scalability and efficiency. Area 0, the backbone area, plays a crucial role in ensuring loop-free route distribution between areas. The following mechanisms are key to preventing routing loops:

Strict adherence to hierarchical area design.

Prohibition of direct inter-area route exchanges between non-backbone areas.

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

Comprehensive and Detailed Step-by-Step Explanation:

1. Multicast Applications:

Multicast is ideal for applications where data is sent from one source to multiple receivers, such as:

Real-Time Audio Conferencing: Multicast delivers audio streams to participants without duplicating the same data for each receiver.

Livestreaming: Streaming live events to viewers using multicast minimizes bandwidth usage by delivering a single stream to multiple users.

Network TV: Multicast is used in IPTV to broadcast TV channels efficiently.

2. Why Data Warehouse is Incorrect:

Data warehouse does not involve point-to-multipoint transmission. Data warehouse activities (e.g., analytics or database queries) typically use unicast connections for communication between the server and the client.

3. Summary:

The correct options are A, B, C, as they all involve point-to-multipoint communication supported by multicast.

In a stateful inspection firewall, if the status detection mechanism is enabled, it tracks and validates the state of connections using the session table. If there is no session table and a SYN+ACK packet reaches the firewall, it checks the security policy. If the policy explicitly permits the packet, it will pass through the firewall, but no session table will be created without the initial SYN packet. The other options are either incorrect or misrepresent the behavior of stateful inspection ​.

 pat

 trust

 12.1.1.0

 inner

Comprehensive and Detailed Step-by-Step Explanation:

ACL Capabilities:

ACLs are versatile tools that can match:

Data packets: Using IP addresses, protocols, ports, etc.

Routes: ACLs can be used in route filtering, matching both IP prefix length and mask length.

Correct Statement:

ACLs can match both the IP address prefix length and mask length in route filtering applications.

References:

HCIA-Datacom Study Guide, Chapter: ACL Applications

Huawei Route Filtering Using ACLs

The summary automatic command in BGP is used to enable automatic summarization of routes, particularly for classful networks. However, manual summarization takes precedence over automatic summarization when both are configured. This makes the statement claiming automatic summarization takes precedence false ​.

OSPF supports both area-level and interface-level authentication. When both are configured, interface authentication takes precedence over area authentication. This hierarchy ensures that specific interface-level configurations override the broader area-level settings when applicable ​.

The prefix list permits the prefix 1.1.1.1/24 with a mask length greater than or equal to /26 and less than or equal to /32. This means only prefixes with the base 1.1.1.1 and mask lengths between /26 and /32 will be permitted. Routes like 1.1.1.2/16 and 1.1.1.1/24 do not meet the mask length criteria, so they will be denied. Conversely, routes like 1.1.1.1/26 and 1.1.1.1/32 satisfy the condition and will be permitted ​.

Comprehensive and Detailed Step-by-Step Explanation:

Analysis of the OSPF Neighbor State:

Router ID 10.0.5.5:

On interface 10.0.235.2 (GigabitEthernet0/0/1), the neighbor state is Full, indicating that adjacency is established.

The Designated Router (DR) is 10.0.235.5, which is the same as the neighbor's address.

Router ID 10.0.4.4:

On interface 10.0.24.2 (Serial1/0/1), the neighbor state is also Full, meaning adjacency is established.

The DR/BDR election status shows None, indicating that the interface is on a point-to-point link where DR/BDR election does not apply.

Validation of Each Option:

Option A: Correct. The DR IP address is explicitly shown as 10.0.235.5.

Option B: Correct. The neighbor state for both 10.0.5.5 and 10.0.4.4 is Full, confirming adjacency is established.

Option C: Incorrect. DR/BDR elections are irrelevant on point-to-point links like Serial1/0/1.

Option D: Correct. The Router IDs of R2's neighbors are explicitly listed as 10.0.5.5 and 10.0.4.4.

References:

HCIA-Datacom Study Guide, Chapter: OSPF Neighbor Relationships

Huawei OSPF Neighbor and Adjacency Details

 GMP Snooping Proxy

IGMP snooping proxy allows the switch to substitute for upstream Layer 3 devices and downstream hosts, reducing unnecessary bandwidth consumption by consolidating IGMP messages.

 HCIP-Datacom-Core Reference

The IGMP snooping proxy functionality is described in multicast optimization and IGMP configuration chapters​​

Comprehensive and Detailed Step-by-Step Explanation:

Definition of Link Aggregation:

Link aggregation combines multiple physical links into a single logical link to improve bandwidth and reliability.

Advantages of Link Aggregation:

Load Balancing (A): Traffic is distributed across all aggregated links to improve performance.

Improved Reliability (B): If one link fails, traffic is rerouted through other links.

Increased Link Bandwidth (C): Bandwidth is effectively the sum of all aggregated links.

Incorrect Option:

Route Backup (D): Route backup is a feature of routing protocols, not link aggregation.

References:

HCIA-Datacom Study Guide, Chapter: Link Aggregation Fundamentals

Huawei Link Aggregation Configuration

Comprehensive and Detailed Step-by-Step Explanation:

1. IPv6 and Neighbor Discovery Protocol (NDP):

In IPv4, a host uses ARP (Address Resolution Protocol) to map an IP address to a MAC address for communication.

In IPv6, ARP is not used. Instead, IPv6 uses the Neighbor Discovery Protocol (NDP) for address resolution.

2. Why the Statement is FALSE:

IPv6 does not use ARP for resolving link-layer addresses.

IPv6 uses NDP, which operates through ICMPv6 messages to perform the equivalent function.

3. Summary:

The statement is FALSE because IPv6 uses NDP, not ARP, to obtain the link-layer address of the destination host.