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 ​.

 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​​.

When the level of an IS-IS interface is changed, the adjacency must be re-established because IS-IS adjacencies are formed based on matching levels (Level-1, Level-2, or both). Other changes, such as cost or hello intervals, do not disrupt the existing adjacency but might impact routing metrics or timing ​.

The traffic limiting policy feature supports not only limiting the number of connections initiated by or received by an IP address but can also apply other traffic metrics such as bandwidth or packet rates. This expanded capability makes the statement false ​.

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 isFALSE.

A is true– MAC authentication often usesPAP or CHAPfor basic password exchange.

B is false– Bydefault, both theusername and password are set to the full MAC addressof the terminal, not just the last 6 digits.

C is true– MAC authentication istransparentto the user and requiresno client softwareon the terminal.

D is true– The authentication system includes:

Terminal(user device),

Access device(AP or switch), and

Authentication server(e.g., RADIUS).

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

“MAC authentication does not require client-side software. By default, both the user name and password are the complete MAC address in lowercase without delimiters.”

(Chapter: WLAN Security – Section: MAC Authentication Mechanism)

 OSPF Authentication Overview

OSPF supports three authentication modes:

Null Authentication: No authentication (default).

Plaintext Authentication: Uses clear-text passwords.

MD5 Authentication: Secure cryptographic authentication.

 Interface-Level Priority

When both interface-level and area-level authentication are configured, OSPF prioritizesinterface-level authentication. This ensures that interface-specific security overrides area-wide configurations for greater granularity and security.

 HCIP-Datacom-Core Reference

OSPF authentication hierarchy and configurations are detailed in the OSPF security configuration chapter​.

The sequence of steps for electing the root port in an STP (Spanning Tree Protocol) network is as follows:

Bridge ID Comparison: TheBridge ID(BID) is compared between the bridges in the network. A smaller value indicates a higher priority, meaning the bridge with the lowest Bridge ID is elected as the root bridge.

RPC (Root Path Cost) Comparison: The path cost to reach the root bridge is calculated. The router with the lowest Root Path Cost (RPC) to the root bridge will have a higher priority for the election of the root port.

Peer BID Comparison: If there is a tie in the Root Path Cost, thePeer BIDis compared. A smaller Peer BID indicates a higher priority. This step ensures that if two routers have the same RPC, the one with the lower Peer Bridge ID wins.

Local BID Comparison: If there is still a tie, theLocal BIDis compared. A smaller Local BID indicates a higher priority. This final step ensures that the router with the lowest local identifier is selected.

Bridge ID Comparison:The first step in electing the root port is comparing the Bridge IDs. The bridge with the lowestBridge IDbecomes theroot bridge. The Bridge ID is made up of thebridge priorityandMAC address. The root bridge is the center of the network for STP, and all other ports will calculate their paths based on this root.

HCIP-Datacom-Core Technology Training Material (STP Concepts and Election Process)​​.

RPC (Root Path Cost) Comparison:Once the root bridge is selected, the network needs to determine the best path to the root. Each port on a non-root bridge will calculate theRoot Path Cost (RPC), which is the cumulative cost of reaching the root bridge from that port. The root port is the one that has the lowest RPC, meaning it provides the best path to the root bridge.

The election of a Designated Router (DR) and Backup Designated Router (BDR) occurs during the OSPF network's initial setup or upon the failure of an existing DR. A new router joining an OSPF network does not automatically preempt the current DR, even if it has the highest priority. DR and BDR elections are not preemptive. The other statements are correct regarding OSPF DR/BDR election processes ​.

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 ​.

Comprehensive and Detailed Step-by-Step Explanation:

1. What is VRF (Virtual Routing and Forwarding)?

VRF is a network virtualization technology that enables multiple isolated routing tables to coexist on a single physical device.

Each VRF instance is independent, which ensures separation between different VPNs or users.

2. Resources That VRF Can Independently Own:

Option A: Interface

Correct.

Each VRF instance can have its own set of interfaces. These interfaces are bound to a specific VRF, isolating traffic at the physical or logical port level.

Option B: Routing table

Correct.

VRF instances maintain independent routing tables. This ensures that routes for one VPN do not overlap or interfere with routes of another VPN.

Option C: MAC address table

Incorrect.

The MAC address table is part of Layer 2 operations and is shared by all VRF instances on the device. VRF operates at Layer 3 and does not isolate MAC address tables.

Option D: Routing protocol process

Correct.

Each VRF instance can run its own routing protocol processes (e.g., OSPF, BGP), and these processes are completely independent of other VRF instances.

3. Summary:

The correct resources that can be independently owned by a VRF instance areInterface,Routing Table, andRouting Protocol Process.

The security policy specifies that traffic originating from12.1.1.2and destined for the untrust zone is permitted. Since the source address of the packet (12.1.1.1) does not match this rule, thepacket matches the default implicit deny rule. However, rule 1 does not deny all other traffic explicitly, so the packet is forwarded based on further configurations ​.

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)

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

HCIP-Datacom-Core Technology Training Material (IS-IS LSPs and Packet Structure)​​.

 LSP ID Format: The LSP ID uniquely identifies each LSP and ensures accurate routing information. It comprises the following components:

System ID (C): A 6-byte identifier assigned to each router, derived from the router's NET (Network Entity Title). This identifier ensures unique identification of routers within the IS-IS domain.

Pseudonode ID (B): Assigned when a router acts as a Designated Intermediate System (DIS) on a broadcast network. It differentiates LSPs generated by the DIS from other routers.

LSP Number (A): A 1-byte field indicating the sequence number of the LSP. It helps distinguish multiple LSPs generated by the same router for the same level.

The Local-Preference attribute is used within an AS to influence outbound traffic paths. The default value is 100, and it is a well-known discretionary attribute, meaning it is not mandatory and does not travel across AS boundaries ​.

Based on the MSTP configuration shown, the role of the switch in MSTI 1 cannot be determined without additional details about the topology or priority values of other switches in the instance. The role could be a root switch, secondary root, or non-root, depending on these factors ​.

Comprehensive and Detailed Step-by-Step Explanation:

IS-IS Three-Way Handshake:

IS-IS uses athree-way handshaketo establish neighbor relationships.

This process is applied on bothpoint-to-point (P2P)andbroadcastnetwork types to confirm bidirectional communication.

P2P Networks:

Routers directly exchange IS-IS Hello (IIH) packets to establish adjacency.

Broadcast Networks:

IS-IS also uses the three-way handshake on broadcast networks to ensure that the Designated Intermediate System (DIS) election and adjacency formation are correct.

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 ​.

RSTP improves convergence by introducing changes to the BPDU handling mechanism and port roles. However, RSTP does not rely on a fixed timeout of four Hello intervals for negotiation failure. Instead, RSTP uses a more dynamic mechanism to detect topology changes. The other options describe valid RSTP improvements ​.

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.

Comprehensive and Detailed Step-by-Step Explanation:

Multi-Channel Protocols:

Multi-channel protocols use separate channels for control and data communication, requiring application-specific packet filtering (ASPF) to track sessions.

Examples:

FTP (A):Uses separate control and data channels.

SIP (B):Uses multiple ports for signaling and media.

H.323 (D):A VoIP protocol using multiple channels.

Single-Channel Protocol:

SMTP (C):A single-channel protocol for email communication, which does not require ASPF.

Comprehensive and Detailed in-depth Step-by-Step Explanation:

BGP (Border Gateway Protocol) uses specific message types to establish and maintain peer relationships between routers. The primary BGP messages involved during the establishment and maintenance of peer relationships are:

Open (D):

The Open message is the first message sent after a TCP connection is established between BGP peers.

It is used to exchange parameters such as the AS number, BGP version, hold time, and BGP identifier.

Keepalive (A):

After the Open message exchange, Keepalive messages are sent periodically to maintain the BGP session.

These messages confirm that the connection is still alive.

Update (C):

Update messages are used to exchange routing information after the peer relationship is established.

They contain information about network prefixes and their associated path attributes.

Hello (B):

Hello messages are not used in BGP. They are typically used in protocols like OSPF or IS-IS to establish and maintain neighbor relationships.

Thus, the correct answers areA (Keepalive),C (Update), andD (Open).

Let’s analyze the process step-by-step:

R1redistributes thedirect route 10.1.1.0/24intoOSPF.

This OSPF route reachesR2andR3.

R2 and R3 are in an environment that usesIS-IStowardsR4.

BothR2 and R3 re-advertisethis OSPF route into IS-IS toward R4 (bidirectional route redistribution).

OnR3, aroute-policy named hcipis applied to controlASE (Autonomous System External) route preference.

The ACL matches the route10.1.1.0/24.

The route-policy sets thepreferenceof this ASE route to14.

InHuawei VRP, if a route-policy applied via preference ase route-policy matches a route, itmodifies the preferencevalue of the redistributed route when it is advertised.

By default:

OSPF ASE routeshave apreference of 150.

But in this case, due to the policy applied, the preference is explicitly changed to14on R3 before re-advertising to R4.

So,R4will install the route10.1.1.0/24from R3 withpreference 14, assuming R2 doesn’t provide a better preference.

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

“You can control the preference of OSPF ASE routes by using a route-policy and applying it with the command preference ase route-policy. When the policy matches, the specified preference is used instead of the default (150).”

(Chapter: OSPF Advanced Features – Section: Route Control and Inter-AS Route Redistribution)

 IGMP:Manages IPv4 multicast group members and runs on the multicast network's last segment (that is, the network segment where a Layer 3 network device is connected to user hosts).

 PIM:Sends multicast data over the network to the multicast device that is connected to group members that have requested the multicast data, implementing multicast data forwarding based on routes.

 IGMP Snooping:Manages and controls the forwarding of multicast data packets to effectively suppress the flooding of multicast data packets on the Layer 2 network.

 IGMP (Internet Group Management Protocol):

IGMP is used by hosts and adjacent multicast routers to establish and maintain multicast group memberships on a local subnet.

It allows a host to inform a multicast router of its desire to receive multicast traffic for a specific group.

It operates at Layer 3 and runs on the last segment of the network.

HCIP-Datacom-Core Technology Training Material (Multicast Fundamentals)​.

 PIM (Protocol Independent Multicast):

PIM is a routing protocol designed for efficient routing of IP multicast traffic. It determines the paths over which multicast packets should be forwarded.

PIM is "protocol-independent" because it uses the underlying unicast routing table for RPF (Reverse Path Forwarding) checks.

It is responsible for distributing multicast data throughout the network.

OptionA is false. When advertising a route to an IBGP peer, theBGP speaker does not modifythe AS_Path. It simply advertises the routeas-is, preserving the AS_Path learned from EBGP.

Clarification of the options:

Bis correct: When a route is sent to an EBGP peer, the local AS is prepended to the AS_Path.

Cis correct: The AS_Path begins with the local AS when a new route is advertised to an EBGP neighbor.

Dis correct: IBGP doesnotmodify AS_Path when passing routes within the same AS.

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

“BGP speakers prepend their AS number to the AS_Path only when advertising to EBGP peers. IBGP peers do not alter the AS_Path.”

(Chapter: BGP Path Attributes – Section: AS_Path)

 Permanent Group Addresses for Routing Protocols

The range224.0.0.0 to 224.0.0.255is 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​​.

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.

A stateful inspection firewall tracks the state of network connections and only matches the initial packet against its rule set. Subsequent packets in the same connection are matched in the statetable. Contrary to this, UDP packets can be inspected by correlating them with connection states, and packets in a single connection are always correlated ​.

The scenario describes a mismatch in OSPF network types between two connected routers: one set to Point-to-Point (P2P) and the other set to Point-to-Multipoint (P2MP). While aligning Hello intervals may seem sufficient for establishing an OSPF neighbor relationship, the fundamental mismatch in network types introduces issues.

OSPF Network Types

P2P: Assumes a direct connection with a single neighbor, uses faster convergence and simpler LSDB synchronization.

P2MP: Supports multiple neighbors on a single interface, requiring different handling for DR/BDR roles and LSDB updates.

Impact of Network Type Mismatch

If Hello intervals are aligned, adjacency establishment might occur. However, mismatched network types affect neighbor role assignment and LSDB synchronization.

P2P expects a direct link and would handle updates differently than P2MP, which assumes multiple neighbors. This leads to inconsistencies in route calculation and forwarding.

HCIP-Datacom-Core Reference

OSPF Basics and Configuration​clearly outlines the criticality of consistent network type configuration for stable OSPF operation.

Lab examples in the HCIP Datacom Lab Guide​further demonstrate the consequences of such mismatches, including unstable neighbor states and incomplete LSDB synchronization.

Hence, the statement that neighbor relationships and LSDB synchronization remain unaffected is incorrect. Proper OSPF operation requires matching network types in addition to aligned Hello intervals.

For first-time configuration of a newly purchased network device, administrators typically use the console port. This direct connection is secure and independent of network configuration, making it suitable for initial setups. Telnet, SNMP, or FTP require prior IP configuration, which is not feasible during the initial setup phase ​.

 Link fault alarm

 The BFD session goes down.

 Interrupted OSPF neighbor relationship

This statement isfalsebecauseIGMPv2 improves upon IGMPv1 by introducing the Leave Group message.

InIGMPv1, members leave silently, and the router waits for the timeout.

InIGMPv2, a host sends aLeave Groupmessage, prompting the router to send aGroup-Specific Queryto determine if other members are still present. If no responses are received, the group is pruned before timeout.

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

“IGMPv2 allows group members to actively send Leave messages, reducing unnecessary forwarding delays. This improves efficiency over IGMPv1.”

(Chapter: Multicast Protocols – Section: IGMP Versions)

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 ​.

 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​​.

Comprehensive and Detailed Step-by-Step Explanation:

1. Understanding LSA Filtering in OSPF and IS-IS:

The filter-policy command is used in OSPF and IS-IS to control which routing information isimported into the local routing tableoradvertised to other neighbors.

However, itcannot filter LSAs forwarded by neighbors. In OSPF and IS-IS, LSAs are always forwarded unchanged within the area to ensure all routers have a consistent link-state database.

Filtering only affects the routes that are installed into the local routing table or advertised to other areas or neighbors.

2. Why the Statement is False:

LSAs are forwarded without being filtered. This ensures link-state protocols maintain the same network topology view across the network.

The filter-policy import command only controls routes that are installed into the local routing table, not the forwarding of LSAs.

3. Summary:

The statement is FALSE because LSAs cannot be filtered by filter-policy import.

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

RFC 2328: OSPF Version 2, LSA Propagation Rules.

Edge ports are used in RSTP to bypass the spanning tree calculation for ports connected to end devices. By configuring ports like SWD's GE0/0/2 and SWC's GE0/0/2 as edge ports, they transition directly to the Forwarding state upon activation, ensuring faster convergence. Statement A is incorrect because receiving BPDU invalidates the edge port status ​.

Comprehensive and Detailed Step-by-Step Explanation:

1. What is the BFD Echo Function?

BFD (Bidirectional Forwarding Detection) is used to detect link failures.

TheEcho functionis an optional feature that tests link connectivity by looping back packets sent from the local device through the forwarding path.

2. Analysis of Each Statement:

Option A: If URPF is enabled on the peer end, BFD packets may be incorrectly discarded on the peer end.

Correct.

URPF (Unicast Reverse Path Forwarding) checks whether the source IP address of an incoming packet is reachable via the interface it was received on. Since the Echo function uses loopback packets, this can conflict with URPF, causing the packets to be dropped.

Option B: In the BFD Echo function, the device uses the IP address of the outbound interface as the source IP address by default.

Correct.

By default, the outbound interface's IP address is used as the source address for BFD Echo packets.

Option C: The BFD Echo function applies only to single-hop BFD sessions.

Incorrect.

The BFD Echo function can be used for both single-hop and multi-hop BFD sessions.

Option D: When configuring a BFD session supporting the BFD Echo function, you need to configure both the local and remote discriminators.

Incorrect.

The BFD Echo function is locally configured and does not require setting remote discriminators. The function operates independently of the remote device's configuration.

3. Summary:

The correct statements areAandB.

IGMP Version Mismatch

If the IGMP snooping version on the device is earlier than the IGMP version on user hosts, the device may fail to parse IGMP Report messages correctly. As a result, the device forwards these messages only to router ports without generating group member ports or forwarding entries.

Consequently, users cannot receive multicast data.

HCIP-Datacom-Core Reference

Multicast and IGMP snooping behaviors under mismatched conditions are described in the multicast configuration chapters​​.

In BGP, theAS-Pathattribute is mandatory and must be included in allUPDATEmessages. It records the autonomous systems a route has traversed. Attributes likeLocal-Preference,MED, andPrefvalare optional and may not always be included. TheAS-Pathis crucial for loop prevention and route selection ​.

 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​​.

Comprehensive and Detailed Step-by-Step Explanation:

BGP Router ID Selection Rules:

If a router ID is not manually configured:

The largest loopback address is selected as the router ID.

If no loopback interfaces exist, the largest active physical interface address is selected.

Default Behavior:

This ensures that a stable and unique router ID is chosen automatically, even without manual configuration.

Policy-Based Routing (PBR) on interfaces is used to forward traffic based on specific policies rather than the routing table. However, PBR is not suitable for modifying the next-hop of locally originated traffic. Other scenarios listed are typical use cases for interface PBR ​.

Option A correctly configures the DHCP relay agent (AC) to forward requests to the DHCP server using VLAN 10.

Option B correctly configures the DHCP server (AR) with the correct IP pool (10.1.1.0/24), gateway, and excluded IP addresses. The static route to10.1.1.0through172.21.1.1ensures proper routing ​.

=========

Comprehensive and Detailed Step-by-Step Explanation:

1. What is GRE (Generic Routing Encapsulation)?

GRE is a tunneling protocol that allows the encapsulation of various types of packets (e.g., IPv4, IPv6, multicast, etc.) to be transmitted over another protocol (e.g., IP).

GRE is used to create point-to-point connections over heterogeneous networks.

2. Analysis of Each Option:

Option A: GRE is a Layer 2 VPN encapsulation technology.

Incorrect.

GRE operates at Layer 3 (Network Layer) and encapsulates Layer 3 packets. It is not a Layer 2 VPN encapsulation technology like MPLS or Ethernet-over-IP.

Option B: GRE enables encapsulated data packets to be transmitted over another network layer protocol, but cannot encapsulate multicast data.

Incorrect.

GRE supports the encapsulation and transmission of multicast data packets. This is one of its key features, making it suitable for protocols like OSPF and multicast applications.

Option C: GRE tunnels can work with IPsec to ensure the security of multicast services such as voice and video.

Correct.

GRE by itself does not provide encryption or security. However, GRE can work with IPsec to secure the encapsulated traffic, including multicast data, for services like voice and video.

Option D: GRE tunnels can extend the working range of network protocols with hop limits.

Correct.

GRE encapsulates packets, effectively resetting their hop limits and allowing protocols with limited hop counts (e.g., RIP) to work over larger networks.

3. Summary:

The correct options areCandD.

BGP, IS-IS, and OSPF support the configuration of default routes through specific command configurations. For example, BGP uses thedefault-originatecommand, IS-IS uses adefault-route-advertisemethod, and OSPF can advertise default routes usingdefault-information originate. ICMP, however, is not a routing protocol and does not support this functionality ​.

The forwarding plane of a switch consists of data forwarding hardware, such as line cards or forwarding engines, and is responsible for tasks like encapsulating/decapsulating packets, providing high-speed data channels, and collecting packet statistics. However, main control boards are part of the control plane, not the forwarding plane. This distinction ensures a separation of data forwarding and control functionalities ​.

A stateful inspection firewall tracks the state of active connections. If a packet matches an existing session in the firewall's state table, it is allowed to pass. The diagram indicates that the TCP packet matches the session state, so the firewall forwards it ​.

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 ​.

 BGP Open Message Components

The Open message contains the following critical parameters:

Local AS Number: The autonomous system of the router.

Router ID: A unique identifier for the router.

Hold Time: The maximum time the router will wait for Keepalive or other messages from its peer.

 Incorrect Option

C. NLRI: Network Layer Reachability Information is not included in Open messages; it is carried in Update messages.

 HCIP-Datacom-Core Reference

The structure and contents of Open messages are explained in BGP protocol details​​.

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 ​.

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.

Huawei HCIA-Datacom Study Guide, Chapter "IP Prefix Lists."

Huawei Configuration Examples for ACL and Prefix Lists.

The prefix list permits the prefix1.1.1.1/24with a mask length greater than or equal to/26and less than or equal to/32. This means only prefixes with the base1.1.1.1and mask lengths between/26and/32will be permitted. Routes like1.1.1.2/16and1.1.1.1/24do not meet the mask length criteria, so they will be denied. Conversely, routes like1.1.1.1/26and1.1.1.1/32satisfy the condition and will be permitted ​.

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.

Comprehensive and Detailed Step-by-Step Explanation:

DHCP Configuration Issues:

Option C:The DHCP function isdisabled by defaulton Huawei devices. If the administrator forgets to enable it, clients cannot receive IP addresses.

Option D:DHCP uses broadcast messages, which do not traverse routers. If the clients and DHCP server are on different subnets, aDHCP relay agentmust be configured.

Other Options:

Option A:Multiple DHCP servers can coexist as long as their IP address pools do not overlap. This is unlikely to cause the problem.

Option B:STP does not affect DHCP operations unless it delays port activation, which is uncommon in this scenario.

Comprehensive and Detailed Step-by-Step Explanation:

1. What is NETCONF?

NETCONF (Network Configuration Protocol) is an XML-based protocol used for network device configuration and management.

It enables reading, modifying, deleting, and restoring configurations programmatically.

2. Supported Operations:

Option A: Modifying configurations

Correct.

NETCONF allows you to modify existing configurations on network devices.

Option B: Deleting configurations

Correct.

Configurations can be deleted using NETCONF operations.

Option C: Restoring configurations

Correct.

NETCONF can restore configurations by applying previously saved configuration data.

Option D: Backing up configurations

Correct.

NETCONF can retrieve and save the current configuration as a backup.

3. Summary:

NETCONF supports all listed operations: modifying, deleting, restoring, and backing up configurations.

The question indicates that a router performs a lookup in its FIB table for a packet and determines that the tunnel ID in the matching entry is 0, suggesting that the packet needs to be forwarded through a tunnel such as an MPLS tunnel. However, this is a misunderstanding of the FIB functionality.

FIB Table OverviewThe Forwarding Information Base (FIB) is used to make packet-forwarding decisions. Entries in the FIB include next-hop information, which can be directly linked to an interface or a tunnel.

If theTunnel IDis0, it indicates that the packet is forwarded via a normal routing path and not through a tunnel.

For MPLS or other tunnels, the Tunnel ID would have a non-zero value pointing to the associated tunnel.

MPLS Tunnel OperationWhen a router forwards packets through an MPLS tunnel, a label-switched path (LSP) is set up. The FIB would reflect specific tunnel identifiers for packets that need such encapsulation.

HCIP-Datacom-Core Reference

Routing Principles and MPLS​explain the forwarding mechanisms clearly, stating that if a packet is routed normally, the tunnel ID remains0.

The section on MPLS​clarifies the encapsulation process and the role of tunnel identifiers.

Hence, the claim in the question is incorrect. A Tunnel ID of0implies no tunneling is required, and normal IP forwarding occurs

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 ​.

Comprehensive and Detailed in-depth Step-by-Step Explanation:

In IS-IS, theinterface costis a metric used to determine the best path to a destination. Lower-cost paths are preferred over higher-cost paths. By default, IS-IS interface costs can range from1 to 63.

Default Cost Range:

IS-IS allows the configuration of interface costs within the range of1–63by default. This range is sufficient for most networks.

Maximum Configurable Cost:

The maximum value that can be configured by default is63. If there is a requirement for a higher cost range, the metric-style can be changed towide, which allows the cost range to extend beyond 63.

Option A (67):Incorrect. 67 is not the maximum default value.

Option B (63):Correct. This is the maximum default cost value.

Option C (64):Incorrect. This is beyond the default range.

Option D (68):Incorrect. This is beyond the default range.

 LSA Lifetime and Deletion

The LS Age field in the LSA header tracks the age of an LSA. When the LS Age reaches its maximum value (3600 seconds), the LSA is marked for deletion. This ensures old or stale LSAs are removed from the network to maintain accurate routing information.

 HCIP-Datacom-Core Reference

Detailed explanation of LS Age behavior and LSA deletion processes can be found in the OSPF LSDB and LSA sections​​.

Comprehensive and Detailed Step-by-Step Explanation:

1. Overview of BFD Optimization:

BFD (Bidirectional Forwarding Detection) is a protocol that provides rapid detection of link failures.

Optimizing BFD involves adjusting parameters to balance between detection speed and network stability.

2. Analysis of Each Statement:

Option A: After a high priority is configured for BFD packets, BFD packets are preferentially forwarded.

Correct (True Statement).

High priority ensures that BFD packets are not delayed or dropped under congestion, improving detection accuracy.

Option B: To quickly learn about the network status and performance requirements, you can set the interval for sending BFD packets to the minimum value.

Incorrect (False Statement).

Setting the interval to the minimum value can lead to excessive BFD session flapping, which may overload the network or cause instability. The interval should be configured based on network requirements and conditions, rather than set to the minimum.

Option C: On a live network, some devices switch traffic only when a BFD session changes to the Up state... configure a delay to compensate for the time difference.

Correct (True Statement).

This is a valid optimization to avoid issues caused by timing mismatches between BFD and routing protocols.

Option D: If a BFD session flaps, master/backup switchovers are frequently performed... set the WTR time.

Correct (True Statement).

The WTR (Wait to Restore) timer helps stabilize BFD by delaying session recovery after a flap, reducing the risk of frequent switchovers.

3. Summary:

The false statement isB, as setting the BFD packet interval to the minimum can destabilize the network.

IGMPv3 builds on IGMPv1 and IGMPv2 by supporting all previous query types, including General Query and Group-Specific Query, while introducing Source/Group-Specific Query. This enhancement allows finer control over multicast group membership ​.

 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.

A is false– Ports in MSTP can havedifferent roles and statesin different MSTIs. Each MSTI can independently elect a root and compute its own topology, which results indifferent port states per MSTI.

B is true– MSTIs use thesame spanning tree algorithm as STP (and RSTP)for calculating the spanning tree topology.

C is true– Each MSTI may have adifferent root bridgeand separate topology, depending on VLAN mappings.

D is true– MSTIs do not independently send BPDUs;only MSTI 0 (CIST)actually sends BPDUs, and information about other MSTIs is encapsulated within it. So thestatement is worded to test conceptual understanding, but not incorrect in MSTP context as framed.

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

“MSTP allows different MSTIs to have different topologies. A port may be forwarding in MSTI 1 but blocking in MSTI 2. This independence improves VLAN-based traffic engineering.”

(Chapter: MSTP Concepts – Section: MSTI Behavior and Port Roles)

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 ​.

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.

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 ​.

Intra-area route calculation in OSPF involves only Router LSAs (Type 1) and Network LSAs (Type 2). Summary LSAs (Type 3) are used for inter-area routes and do not participate in intra-area route calculation. Therefore, the statement is false ​.

 Additional Port Roles in MSTP

Master Port: Indicates the port on the shortest path to the root bridge in a region.

Regional Edge Port: Identifies a port at the boundary of the MST region.

Backup and edge ports exist in RSTP and are not newly introduced by MSTP.

 HCIP-Datacom-Core Reference

MSTP port roles are elaborated in the MSTP configuration sections​​.

The Link State ID in a Type 3 LSA (Summary LSA) indicates the network or subnet being summarized, not the router ID of an ABR. All other statements accurately describe OSPF functionality, making D the false statement ​.

 LSP Generation in IS-IS

IS-IS routers generate new Link State Packets (LSPs) under the following conditions:

Interface Status Changes: When IS-IS interfaces go up or down, the link state changes, triggering LSP updates.

Periodic Updates: IS-IS periodically regenerates LSPs to ensure link-state information remains synchronized across the network.

Interface Metric Changes: Any modification to interface costs results in a new LSP to reflect the updated cost in the network.

 Incorrect Option

C. Inter-area IP routes change is incorrect because IS-IS does not inherently differentiate between areas for LSP generation.

 HCIP-Datacom-Core Reference

IS-IS LSP generation rules are detailed in the IS-IS configuration and implementation chapters​​.

By default, a router interface sends PIM (Protocol Independent Multicast) Hello messages every 30 seconds to maintain neighbor relationships. This interval can be adjusted using configuration commands ​.

A is false– Thedefault value of Local_Pref is 100, not 0.

B is false–Local_Pref is not advertised to EBGP peers, it is only sent toIBGP peers.

C is correct– TheLocal_Pref value stays constantunless modified by a route-policy or filter.

D is correct–Higher Local_Pref values indicate preferred paths, so BGP prefers the path with the highest Local_Pref among multiple options.

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

“Local_Pref is used to select the best outbound path for traffic leaving the AS. It is only shared among IBGP peers and defaults to 100. The higher the value, the more preferred the route.”

(Chapter: BGP Path Attributes – Section: Local Preference)

Comprehensive and Detailed Step-by-Step Explanation:

BGP ConnectRetry Timer:

The ConnectRetry timer is used when establishing a TCP connection between BGP peers.

If the connection is successful, the timer is disabled.

If the connection fails, the timer restarts, and the router attempts to reconnect after the timer expires.

Behavior:

This timer prevents excessive connection attempts and ensures efficient resource utilization.

1 – Idle

2 – Connect

3 – OpenSent

4 – OpenConfirm

5 – Established

6 – Active

TheBGP finite state machinedefines how a BGP speaker transitions through various states when establishing and maintaining a BGP session. Below is the role of each state:

Idle (1)– BGP is waiting to start a connection. Initial state of the BGP process.

Connect (2)– BGP initiates a TCP connection to the peer.

OpenSent (3)– TCP connection is established; BGP sends an OPEN message and waits for one from the peer.

OpenConfirm (4)– BGP has received a valid OPEN message and is now expecting a KEEPALIVE.

Established (5)– BGP session is fully established; UPDATE messages can now be exchanged.

Active (6)– If the TCP connection fails in Connect state, BGP transitions to Active and will retry connection.

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

“BGP goes through the following states in order: Idle → Connect → Active → OpenSent → OpenConfirm → Established. The transition depends on the success or failure of TCP connection setup and BGP message exchanges.”

(Chapter: BGP Principles – Section: BGP State Machine)

The default sending interval for BFD (Bidirectional Forwarding Detection) control packets is 100 milliseconds. This interval ensures rapid detection of link faults, providing fast failover and minimizing downtime in network operations ​.

Comprehensive and Detailed Step-by-Step Explanation:

1. Single-Hop BFD Session:

A single-hop BFD session is used to detect link failures between directly connected devices.

It is bound to thelocal IP addressand thepeer IP address, and the session relies on these parameters to establish connectivity.

2. Why Modifications Require Deletion:

BFD sessions are tightly bound to their configuration parameters (e.g., local and peer IP addresses).

Modifying these parameters is not supported for an existing session. Instead, you must delete the session and recreate it with the updated parameters.

3. Why the Statement is TRUE:

The statement correctly describes the behavior of BFD sessions, where modifying an existing session is not possible without deleting it first.

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 ​.

Comprehensive and Detailed in-depth Step-by-Step Explanation:

In an Intermediate System to Intermediate System (IS-IS) network, aDesignated 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 theDIS priorityvalue, which is configured on IS-IS interfaces. If two routers have the same priority, the router with the higher MAC address becomes the DIS.

Thedefault DIS priorityfor IS-IS interfaces is64, 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.

Comprehensive and Detailed in-depth Step-by-Step Explanation:

BGP confederations are used to reduce the complexity of IBGP full-mesh connections within a large AS by dividing the AS into multiple sub-ASs (called "member ASs") while still appearing as a single AS to external ASs. Below is an analysis of each option:

A. The ASs outside a confederation still consider the confederation as one AS:

This istrue.Externally, the entire confederation is seen as a single AS, identified by the main AS number.

B. After a confederation is configured, the original IBGP attributes can be retained:

This istrue.The configuration of a confederation does not affect the IBGP attributes exchanged between routers.

C. After a confederation is configured, the original AS number is used as the confederation ID of each router:

This istrue.The main AS number is used as the Confederation Identifier for all member ASs in the confederation.

D. A confederation divides an AS into several sub-ASs, and EBGP full-mesh connections are established in each sub-AS:

This isfalse.Within each sub-AS of a confederation,IBGP connectionsare still used (not EBGP). Confederations are designed to reduce the number of IBGP full-mesh connections required within a large AS by creating smaller, manageable sub-ASs.

Therefore, the correct answer isD.

Thesummary automaticcommand 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 ​.

Comprehensive and Detailed Step-by-Step Explanation:

BGP Router ID Behavior:

The router ID uniquely identifies a BGP device in the network.

If the router ID is changed, it is equivalent to creating a new BGP instance, and the existing BGP session is reset to establish a new peer relationship.

Impact of Router ID Change:

BGP peering relies on stable identifiers. Changing the router ID disrupts the TCP session and requires reestablishing the relationship.

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 ​.

A stateful inspection firewall tracks the state of network connections and only matches the initial packet against its rule set. Subsequent packets in the same connection are matched in the state table. Contrary to this, UDP packets can be inspected by correlating them with connection states, and packets in a single connection are always correlated ​.

Comprehensive and Detailed Step-by-Step Explanation:

Analysis of BGP Attributes:

Original Next Hop:The output shows that the original next hop of the route is 172.16.1.2. (A is correct).

Local Router ID:The local BGP router ID is 10.1.1.1, as displayed. (B is correct).

Local AS Number:The local AS number is 100, as displayed. (C is correct).

Incorrect Option:

Local_Pref:Although Local_Pref is an important attribute, this route is marked as invalid due to "IP unreachable" and thus cannot be preferentially selected.