H12-821_V1.0 Sample Questions Answers

 Edge Port Behavior

An edge port transitions directly to the Forwarding state but reverts to participating in RSTP calculations if it receives a valid configuration BPDU. Thus, statement C is false.

 HCIP-Datacom-Core Reference

The behavior of edge ports and their transitions are discussed in the RSTP enhancement sections​​.

 Silent Interface Explanation

The silent-interface command is used to prevent OSPF from sending or receiving OSPF packets on the specified interface (GE 0/0/1). This disables OSPF adjacency establishment and stops route advertisement for that interface.

 Network Observations

Statement A: R2 can access the server.This is correct, as the silent interface does not impact data traffic, only OSPF-related communication.

Statement B: GE 0/0/1 of R1 cannot send OSPF packets.Correct due to the silent-interface configuration.

Statement C: The network segment to which GE 0/0/1 of R1 belongs cannot be advertised.This is correct, as the silent interface prevents route advertisement.

Statement D: GE 0/0/1 of R1 cannot accept OSPF packets.Correct, as the silent interface configuration blocks packet reception.

 HCIP-Datacom-Core Reference

OSPF interface command behavior is outlined in the configuration and lab examples sections​​.

After Layer 3 roaming, the STA’s traffic is forwarded from the Foreign AP (FAP) to the Foreign AC (FAC), and then to the Home AC (HAC) before reaching the upper-layer network. This ensures that the STA remains on the same subnet without breaking existing sessions ​.

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 ​.

The Originator ID in a BGP route represents the Router ID of the device that originally advertised the route into the BGP domain. Since RTA originates the route 10.1.1.0/24 into the BGP process, the Originator ID in the route received by RTD will be set to 1.1.1.1 ​.

Comprehensive and Detailed in-depth Step-by-Step Explanation:An Area Border Router (ABR) is an OSPF router that connects multiple areas, including the backbone area (Area 0). It plays a critical role in summarizing and propagating routing information between areas. The types of LSAs that an ABR can generate include:

Network Summary LSA (Type 3):

ABRs generate Type 3 LSAs to summarize and propagate routes from one area into another.

For example, an ABR generates a Type 3 LSA to inform other areas about the networks in the area it is connected to.

ASBR Summary LSA (Type 4):

If an ASBR exists in one of the OSPF areas connected to the ABR, the ABR generates Type 4 LSAs.

These LSAs provide information about how to reach the ASBR.

NSSA LSA (Type 7):

If the ABR is connected to a Not-So-Stubby Area (NSSA), it can generate Type 7 LSAs.

These LSAs are used to describe external routes imported into the NSSA.

AS External LSA (Type 5):

These LSAs are not typically generated by an ABR unless the ABR is also functioning as an ASBR. Type 5 LSAs are used to describe external routes imported into OSPF from other autonomous systems.

Therefore, NSSA LSA (A), Network Summary LSA (C), and ASBR Summary LSA (D) are valid answers. AS External LSA (B) would only be correct if the ABR were also functioning as an ASBR, but that is not explicitly stated in the question.

References:

Huawei HCIA-Datacom Study Guide, Chapter on "OSPF LSAs and ABR Functions".

RFC 2328 – OSPF Version 2.

Comprehensive and Detailed In-Depth Explanation:

Intermediate System to Intermediate System (IS-IS) routers send IS-to-IS Hello (IIH) packets to establish neighbor relationships.

The Reserved/Circuit Type field in IIH packets indicates which level of IS-IS adjacency the router is trying to establish:

00 → Level-0 (Not used in IS-IS).

01 → Level-1 router.

10 → Level-2 router.

11 → Level-1-2 router (Both levels supported).

Since the question asks for the field value in an L1-L2 router’s IIH packets, the correct answer is 11 (B).

???? Reference: Huawei HCIA-Datacom Study Guide, IS-IS Neighbor Discovery and IIH Packet Format.

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.

References:

HCIA-Datacom Study Guide, Chapter: BGP Routing Attributes

Huawei BGP Routing Table Analysis

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 In-Depth Explanation:

A NET (Network Entity Title) consists of three parts:

Area Address → Identifies the IS-IS area.

System ID → Uniquely identifies the router.

SEL (NSEL - N-selector) → Always 0 in IS-IS.

The Area Address part contains:

AFI (Authority and Format Identifier) → Identifies the address type.

IDI (Initial Domain Identifier) → Identifies the routing domain.

System ID is NOT part of the Area Address, so the correct answers are B (AFI) and C (IDI).

???? Reference: Huawei HCIA-Datacom Study Guide, IS-IS Addressing and NET Structure.

 VRRP and BFD Association:

VRRP (Virtual Router Redundancy Protocol) is used to provide gateway redundancy by electing a master and backup router.

Associating VRRP with BFD (Bidirectional Forwarding Detection) allows faster detection of faults on the master device or the link between the master and the backup.

 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.

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.

By default, Huawei firewalls create security zones such as Trust, Untrust, and Local. The DMZ (Demilitarized Zone) is a security zone explicitly created by users. A DMZ is used to isolate an internal network from the external one, providing an additional layer of security by placing public-facing services (e.g., web servers) in this intermediary zone. This setup ensures that if a public-facing service is compromised, the internal network remains secure. Huawei Firewall configuration steps confirm this zoning principle, making DMZ creation an explicit user-driven action ​.

Comprehensive and Detailed In-Depth Explanation:

STP Port Roles:

Root Port (RP) → Connects directly to the Root Bridge.

Designated Port (DP) → Forwards traffic for a given segment.

RSTP introduces two additional roles to improve redundancy:

Backup Port → A redundant Designated Port (on the same switch).

Alternate Port → A backup Root Port (path to the Root Bridge).

All four roles exist in RSTP, making the correct answer A, B, C, D.

???? Reference: Huawei HCIA-Datacom Study Guide, RSTP Port Roles and Rapid Convergence.

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 are Interface, Routing Table, and Routing Protocol Process.

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 ​.

Comprehensive and Detailed Step-by-Step Explanation:

1. Understanding IGMP Version Compatibility:

IGMP (Internet Group Management Protocol) supports multiple versions, such as IGMPv1, IGMPv2, and IGMPv3.

A device running a later version of IGMP is backward-compatible and can identify Report messages from earlier versions.

However, a device running an earlier version of IGMP cannot recognize the newer features or formats of later IGMP versions.

2. Best Practice:

To avoid compatibility issues, the IGMP version configured on the switch should be the same as or later than the version used by the member hosts in the network.

3. Why the Statement is TRUE:

The statement is correct because it describes the compatibility behavior of IGMP versions and advises setting the switch IGMP version appropriately.

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

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

Comprehensive and Detailed In-Depth Explanation:

When a packet is checked against an Access Control List (ACL), it is processed based on rule matches.

"Unmatched" scenarios occur if:

A. TRUE → The packet does not match any ACL rule.

C. TRUE → No ACL is configured, so there are no rules to match.

D. TRUE → An empty ACL exists, meaning no rules are defined.

B is incorrect because if the packet matches a deny rule, it is "matched" and explicitly dropped, not "unmatched".

???? Reference: Huawei HCIA-Datacom Study Guide, ACL Rule Matching and Processing Logic.

Comprehensive and Detailed Step-by-Step Explanation:

BGP Origin Attribute Priority:

The Origin attribute determines the source of the route and affects the selection of the best path.

The priority order is as follows:

IGP (i): Highest priority. Routes injected using the network command.

EGP (e): Lower priority. Routes learned from the EGP protocol.

Incomplete (?): Lowest priority. Routes redistributed into BGP from other protocols.

Correct Option:

A: IGP > EGP > Incomplete is the correct order of priority.

References:

HCIA-Datacom Study Guide, Chapter: BGP Path Selection

Huawei BGP Routing Rules

Comprehensive and Detailed Step-by-Step Explanation:

IGMPv1 Querier Selection:

In IGMPv1, there is no built-in querier election mechanism. Querier selection depends on the multicast routing protocol (e.g., PIM).

IGMPv2 and IGMPv3 Querier Selection:

In IGMPv2 and IGMPv3, the router interface with the largest IP address in the multicast group is selected as the querier.

Correct Statement:

The statement accurately describes the querier selection mechanisms in IGMP versions.

References:

HCIA-Datacom Study Guide, Chapter: IGMP Querier Mechanism

Huawei Multicast Protocol Comparison

Comprehensive and Detailed In-Depth Explanation:

STP (Spanning Tree Protocol) BPDUs do not contain an explicit port role field. Instead, roles are determined indirectly.

RSTP (Rapid Spanning Tree Protocol) modifies BPDU structure by using the Flags field to indicate:

Port roles (Root, Designated, Alternate, Backup)

Proposal/Agreement (P/A) handshake mechanism

The correct field that specifies the port role in RSTP BPDUs is Flags.

???? Reference: Huawei HCIA-Datacom Study Guide, RSTP BPDU Structure and Flags Field.

 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.

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

Comprehensive and Detailed Step-by-Step Explanation:

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.

References:

HCIA-Datacom Study Guide, Chapter: BGP Session Establishment

Huawei BGP Timers and Session Management

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 ​

Comprehensive and Detailed In-Depth Explanation:

Wireless LAN (WLAN) roaming allows mobile devices (STAs) to move seamlessly between different APs without dropping connections.

Types of WLAN Roaming:

Layer 2 roaming → STAs move between APs in the same subnet without IP address changes.

Layer 3 roaming → STAs move across different subnets, requiring IP address reconfiguration (handled via DHCP or tunneling).

Since roaming prevents service interruption in large WLAN deployments, the statement is true.

???? Reference: Huawei HCIA-Datacom Study Guide, WLAN Roaming and Seamless Connectivity.

 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​​.

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 ​.

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 ​.

 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 In-Depth Explanation:

A. TRUE → The interface GigabitEthernet0/0/1 has an IP address of 192.168.1.1.

B. TRUE → The IGMP version is explicitly stated as IGMPv2.

C. TRUE → The maximum query response time for IGMP is set to 10 seconds.

D. TRUE → The IGMP Query Interval is configured as 60 seconds, meaning the router sends Group-Specific Queries every 60 seconds.

???? Reference: Huawei HCIA-Datacom Study Guide, IGMP Configuration and Query Timers.

 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 given topology, the route from R4 to 10.0.2.2/32 traverses R3, which performs route leaking from Level-2 to Level-1. The cost is calculated as follows: R4 to R3 (40) + R3 to R2 (10) + R2 to the destination (30), resulting in a total cost of 80 ​.

 In asynchronous mode, BFD control packets are exchanged periodically to detect faults.

 In demand mode, once the session is established, BFD stops sending periodic control packets and relies on external mechanisms to verify connectivity.

 Asynchronous mode is the most commonly used mode. However, the Echo function is supported in asynchronous mode, making Option B incorrect ​.

Comprehensive and Detailed Step-by-Step Explanation:

IPv4 Address Classes:

Class D: Reserved for multicast and defined by the first four bits as 1110.

Address range: 224.0.0.0 to 239.255.255.255.

Structure:

Class D does not include a network/host division, as it is designed for group communication rather than device identification.

References:

HCIA-Datacom Study Guide, Chapter: IPv4 Address Classes

Huawei Multicast Configuration Guidelines

Let me continue with the next set of questions!

DIS Election in IS-IS:

In IS-IS, the Designated Intermediate System (DIS) is elected on broadcast networks to reduce the number of LSAs exchanged and maintain the LSDB.

The DIS is elected based on priority:

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

If priorities are equal, the System ID is used as a tie-breaker, and the router with the highest System ID becomes the DIS.

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 ​.

 GRE Characteristics

GRE does not inherently support encryption or authentication. It is a tunneling protocol for encapsulating packets, and data security features must be implemented using other protocols such as IPsec.

Other correct attributes of GRE include:

B. Supports multicast transmission.

C. Acts as a Layer 3 VPN encapsulation technology.

D. Can work with VPN protocols like IPsec for better security.

 HCIP-Datacom-Core Reference

GRE features and limitations are discussed in VPN encapsulation technology chapters​​.

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

Wi-Fi 6 corresponds to the IEEE 802.11ax standard. It offers improved efficiency, higher data rates, and better performance in dense environments compared to its predecessors like 802.11ac (Wi-Fi 5) and 802.11n (Wi-Fi 4) ​.

Comprehensive and Detailed In-Depth Explanation:

IPsec (IP Security Protocol) establishes Security Associations (SAs) for encrypted communication.

An SA is uniquely identified by a 3-tuple:

SPI (Security Parameter Index) → Identifies the SA.

Destination IP Address → Specifies the receiving device.

Security Protocol ID → Indicates whether AH (Authentication Header) or ESP (Encapsulating Security Payload) is used.

A. Key exchange protocol is not part of the SA 3-tuple. It is used during IKE (Internet Key Exchange) but is not part of the SA itself.

???? Reference: Huawei HCIA-Datacom Study Guide, IPsec Security Association and SA Identification.

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.

References:

HCIA-Datacom Study Guide, Chapter: BGP Peer Relationships

Huawei BGP Configuration Best Practices

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.

The command output confirms that the VLANs with IDs 2 and 4 are part of the VLAN pool named "STA." The VLAN pool concept is used to allocate VLANs dynamically to devices or subnets, which reduces broadcast domain size and improves network efficiency. The total number of VLAN pools is unrelated to this output, and the assignment algorithm (hash or even) is not explicitly mentioned in the output. Huawei VLAN pool management references align with this analysis ​.

1 → A Startup message with a priority of 255 is received.2 → A Startup message with a priority less than 255 is received.3 → A Shutdown message is received.4 → The Master_Down timer expires, an Advertisement packet with the priority of 0 is received, or a packet with a priority lower than the local priority is received.5 → A packet with a priority higher than the local priority is received.6 → A Shutdown message is received.

???? Reference: Huawei HCIA-Datacom Study Guide, VRRP Status Transitions.

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Explanation of Root Port Election in STP:

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

Steps for Root Port Election in Sequence:

RPC Comparison (Root Path Cost):

The port with the lowest Root Path Cost is preferred.

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

Peer BID (Bridge ID) Comparison:

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

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

Peer PID (Port ID) Comparison:

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

The port connecting to the lower Port ID is preferred.

Local PID (Port ID) Comparison:

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

The port with the lower Local Port ID is selected.

In asynchronous mode, two devices exchange BFD Control packets to monitor connectivity. However, this mode does support the echo function, which tests bidirectional paths by sending packets that loop back to the origin. This statement is incorrect. Demand mode, on the other hand, minimizes the control packet exchange, relying on periodic echo packets if configured. Huawei's BFD configuration guides emphasize these distinctions ​.

 Transitive vs. Non-Transitive Attributes

The Community attribute is a transitive optional attribute, meaning that if a router receives a route with this attribute and does not understand its purpose, the router retains and propagates it to other peers.

Other options, such as AS_Path and MED, are well-defined mandatory or optional attributes with specific purposes.

 HCIP-Datacom-Core Reference

The behavior of optional transitive attributes is detailed in the BGP protocol and attribute chapters​​.

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

Comprehensive and Detailed In-Depth Explanation:

OSPF uses Hello packets to establish and maintain neighbor relationships. The method of sending Hello packets depends on the network type:

Broadcast networks (e.g., Ethernet) use multicast (224.0.0.5) to discover and maintain OSPF neighbors.

Point-to-Point (P2P) networks (e.g., PPP links) also use multicast (224.0.0.5) for Hello packet exchange.

Non-Broadcast Multi-Access (NBMA) networks (e.g., Frame Relay) require manual neighbor configuration and use unicast Hello packets instead of multicast.

Point-to-Multipoint (P2MP) networks can send Hello packets either unicast or multicast, but it depends on configuration.

???? Reference: Huawei HCIA-Datacom Study Guide, OSPF Neighbor Discovery and Hello Packet Mechanism.

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

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

Comprehensive and Detailed Step-by-Step Explanation:

Definition of the Origin Attribute:

The Origin attribute is a well-known mandatory attribute used to indicate the source of a route. It has three possible values:

i (IGP): The route was injected into BGP using the network command.

e (EGP): The route was learned from an EGP protocol (not commonly used now).

? (Incomplete): The route was redistributed into BGP from another routing protocol.

Analysis of Each Option:

Option A: Correct. When the network command is used, the Origin is set to i (IGP).

Option B: Incorrect. Routes learned from EGP have the Origin attribute set to e (EGP), not ? (Incomplete).

Option C: Correct. BGP prefers routes with the Origin attribute in the order: IGP > EGP > Incomplete.

Option D: Correct. The Origin attribute is a well-known mandatory attribute.

References:

HCIA-Datacom Study Guide, Chapter: BGP Attributes

Huawei BGP Attribute Comparison

ICMPv6 messages are classified into two types: error messages (e.g., Destination Unreachable, Time Exceeded) and informational messages (e.g., Echo Request, Echo Reply). This classification is fundamental to ICMPv6's operation ​.

Routing policies are used to control how routes are imported, advertised, or received. Policy-Based Routing (PBR) is used to forward packets based on policies, bypassing the routing table. Routing policies are not used for packet forwarding ​.

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 ​.

By default, BGP does not automatically summarize imported routes. Route summarization must be explicitly configured using the summary or similar commands ​.

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

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 ​.

LS Ack (Link State Acknowledgment) packets are used to acknowledge received LSAs and do not contain complete LSA information. Instead, they contain only the headers of LSAs being acknowledged. This contrasts with LS Update packets, which carry full LSA details. The misunderstanding of LS Ack functionality makes this statement false ​.

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 ​.

The Designated Intermediate System (DIS) in an IS-IS broadcast network sends Complete Sequence Number PDUs (CSNPs) at a default interval of 30 seconds. This interval ensures periodic synchronization of the Link State Database (LSDB) among IS-IS neighbors ​.

The DHCPNAK message is sent by the DHCP server to the client to indicate that the requested configuration is not valid. Messages like DHCPDiscover, DHCPRequest, and DHCPRelease are initiated by the client in the DHCP process ​.

Comprehensive and Detailed In-Depth Explanation:

IP Multicast vs. Broadcast:

A. TRUE → Unlike broadcast, which sends data to all hosts in a subnet, multicast only sends data to interested receivers, preventing flooding.

B. TRUE → Multicast optimizes bandwidth usage by sending a single copy of data, which is then replicated at network routers only when necessary.

IP Multicast vs. Unicast:

C. FALSE → Multicast does not improve security; it may expose data to unintended receivers if not properly controlled.

D. FALSE → Multicast reduces the load on the source because a single data stream serves multiple receivers instead of sending individual unicast streams.

???? Reference: Huawei HCIA-Datacom Study Guide, IP Multicast Principles and Benefits.

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 is B, as setting the BFD packet interval to the minimum can destabilize the network.

 Export Routing Policy Changes

When an export routing policy is modified, BGP does not automatically resend affected routes. Manual intervention, such as a clear ip bgp command, is required to resend Update messages reflecting the new policy.

 Incorrect Options

B. IGP routes can also be advertised into BGP using redistribution, not just the network command.

C. A router can be configured with multiple BGP processes using different AS numbers (multi-instance BGP).

D. Open messages carry additional parameters such as AS number, Hold Time, and Router ID, not just the header.

 HCIP-Datacom-Core Reference

BGP policy and update behavior are detailed in the route control and redistribution chapters​​.

An IP prefix filter is designed to match both the IP address and its prefix length, making it suitable for filtering routing information rather than data packets. Options A and D are incorrect because IP prefix filters do not work directly on data packets, and they can match both prefix numbers and lengths ​.

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 ​.

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 ​.

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.

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 ​.

 ACL in Routing Policies

ACLs are frequently used in routing policies to match specific routes based on criteria such as source IP, destination IP, and more. This allows ACLs to influence route redistribution, filtering, and forwarding decisions.

 HCIP-Datacom-Core Reference

ACL applications in routing policies are discussed in the routing policy chapters​​.

Comprehensive and Detailed Step-by-Step Explanation:

IS-IS Three-Way Handshake:

IS-IS uses a three-way handshake to establish neighbor relationships.

This process is applied on both point-to-point (P2P) and broadcast network 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.

References:

HCIA-Datacom Study Guide, Chapter: IS-IS Adjacency Establishment

Huawei IS-IS Network Configuration

SSL VPN and Its Functionality:

SSL VPN (Secure Sockets Layer Virtual Private Network) provides secure remote access to a network using SSL/TLS protocols.

SSL VPN operates at the Application Layer of the OSI model. It enables secure communication for applications like web browsers, email clients, and file sharing.

Unlike IPsec VPN, which operates at the Network Layer, SSL VPN focuses on application-specific encryption and authentication.

Comprehensive and Detailed In-Depth Explanation:

SSH (Secure Shell) provides secure remote login and data encryption over insecure networks.

A. TRUE → SSH requires user authentication before access is granted.

B. TRUE → Enabling SSH opens listening ports, which could be scanned by attackers. Proper security measures (e.g., disabling unused SSH access) are recommended.

C. TRUE → ACLs can be applied to VTY (Virtual Terminal) lines to restrict SSH access based on IP addresses.

D. FALSE → The default SSH server port is 22, not 23. Port 23 is used for Telnet, which is less secure than SSH.

???? Reference: Huawei HCIA-Datacom Study Guide, SSH Configuration and Security Measures.

 BGP Keepalive Message Behavior

Keepalive messages are used to maintain the Established state of a BGP peer relationship.

The Keepalive timer determines the frequency of these messages and defaults to 60 seconds, as per the BGP specification.

 HCIP-Datacom-Core Reference

The Keepalive timer default value is covered in the BGP configuration and operational principles​​.

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​​.

 pat

 trust

 12.1.1.0

 inner

For single-hop BFD (Bidirectional Forwarding Detection), the configuration must include the local and remote discriminators to uniquely identify the session endpoints. Additionally, enabling BFD globally is a prerequisite for initiating BFD sessions. Configuring multicast IP addresses is unnecessary for single-hop BFD, as it operates over direct links. Huawei's configuration guidelines specify these requirements to ensure effective deployment and operation of BFD​​.

 Understanding BFD (Bidirectional Forwarding Detection):

BFD is a protocol used to detect link faults quickly between two routers.

Single-hop BFD operates on directly connected links and is commonly used for fast fault detection in routing protocols like OSPF and BGP.

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.

The hardware modules of Huawei modular devices and their functions are:

Main Processing Unit (MPU): Provides control and management planes for the entire system, responsible for protocol processing, system security, and software upgrades.

Switch Fabric Unit (SFU): Provides the data plane, enabling high-speed data switching between service modules.

Line Processing Unit (LPU): Manages data forwarding, offering various interfaces (optical and electrical) for data access​​.

AI-driven networks focus on maximizing efficiency by minimizing latency to enhance data processing and decision-making speed. The AI era emphasizes leveraging large data volumes and ensuring rapid data center interconnectivity. This makes low latency a critical requirement for AI-ready data center networks, as highlighted in Huawei's AI and data center network optimization materials ​.

Comprehensive and Detailed In-Depth Explanation:

SNMP (Simple Network Management Protocol) v3 is a more secure version of SNMP, supporting authentication and encryption.

If the NMS is not receiving SNMPv3 traps, possible causes include:

A. FALSE → The SNMP version mismatch does not affect traps; devices can send SNMPv2 traps even when using SNMPv3.

B. TRUE → If the SNMPv3 password is incorrect, authentication will fail, and traps will not be processed by the NMS.

C. FALSE → The size of packets sent by the NMS does not affect incoming SNMP traps from the router.

D. TRUE → The community name must match on both the NMS and the router, or traps will be ignored.

???? Reference: Huawei HCIA-Datacom Study Guide, SNMPv3 Configuration and Authentication.