H12-821_V1.0 HCIP-Datacom-Core Technology V1.0 Questions and Answers

Comprehensive and Detailed Step-by-Step Explanation:

WAN Definition:

A WAN is a large-scale network spanning a wide geographical area, connecting smaller networks such as LANs and MANs.

Use Cases:

WANs are commonly used for interconnecting campus networks, branch offices, and data centers over long distances.

Correct Statement:

The statement accurately describes the purpose and scope of WANs.

Comprehensive and Detailed Step-by-Step Explanation:

ACL Capabilities:

ACLs are versatile tools that can match:

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

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

Correct Statement:

ACLs can matchboth the IP address prefix length and mask lengthin route filtering applications.

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.

The information provided indicates that the configured query interval is 60 seconds, which applies to general queries. Group-specific queries are sent at a shorter interval, usually derived from the maximum response time. Therefore, the statement about a 60-second interval for group-specific queries is false. Other statements regarding maximum response time (10s), IP address, and IGMP version (V2) are correct ​.

Comprehensive and Detailed Step-by-Step Explanation:

Firewall Session Table:

A session table is used to track active sessions. If a session remains idle for longer than the configured aging time, it is removed to free resources and enhance security.

TCP Session Timeout:

If the interval between two packets exceeds the session timeout, the firewall deletes the session information, requiring the session to be re-established.

Comprehensive and Detailed In-Depth Explanation:

Stub areasdo not allowexternal routes(Type 5 LSAs).

SinceASBRs are responsible for redistributing external routesinto OSPF, theycannot exist in a stub area.

If an ASBR were placed in a stub area, it would attempt to inject external routes into the OSPF domain, which contradicts the stub area rules.

To allow external routes,Not-So-Stubby Areas (NSSAs)are used instead, which allowASBRsand useType 7 LSAsto carry external routes.

????Reference:Huawei HCIA-Datacom Study Guide, OSPF Area Types and ASBR Restrictions.

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 ​.

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 Step-by-Step Explanation:

Routing Table Structure:

Routers maintain a localcore routing tableand separateprotocol routing tablesfor OSPF, BGP, etc.

The local core routing table storesoptimal routesselected 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.

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

TheNetwork Entity Title (NET)is a unique identifier assigned to an IS-IS router. It is derived from theNetwork Service Access Point (NSAP)address and consists of the following components:

Area Address:

Identifies the area in which the router resides.

Multiple routers in the same IS-IS area must have the same area address.

System ID:

Uniquely identifies the router within the IS-IS area.

The System ID is typically derived from the router's loopback IP address or another unique value.

SEL (Selector Field):

The SEL field is always set to00for IS-IS NETs.

The NET is used by IS-IS for route calculation and to identify the router within the IS-IS domain. Therefore, the statement isTRUE.

The error indicates "Incorrect remote AS," which refers to a mismatch in the autonomous system (AS) numbers during BGP peer configuration. This issue is unrelated to the neighbor address. The neighbor address (10.1.1.5) and timestamp (2010-03-22 12:40:39) provided in the output are correct, and the error type confirms a neighbor relationship issue ​.

Comprehensive and Detailed Step-by-Step Explanation:

Session Creation in Firewalls:

Firewalls create session entries for packets requiring stateful inspection (e.g., TCP, UDP, ICMP, and GRE).

Subsequent fragmentsof large packets do not require new sessions. Instead, they are processed based on the session created for the first fragment.

Correct Option:

C (Subsequent Fragment):Does not trigger a new session entry as it belongs to an existing session.

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

To understand this question, let's first review the functional planes in network devices, particularly Huawei switches:

Control Plane:

The control plane is responsible for generating and maintaining routing tables and forwarding entries.

It uses protocols like OSPF, BGP, and RIP to exchange routing information with other network devices. Once the routing information is processed, it installs forwarding entries into the forwarding plane for actual packet forwarding.

On Huawei switches, the control plane is mandatory for building and updating the forwarding table. Without it, the data plane cannot forward traffic correctly.

Forwarding Plane (or Data Plane):

This plane handles the actual forwarding of packets based on the forwarding table created by the control plane.

The forwarding plane operates at high speed to ensure that traffic flows efficiently.

Monitoring Plane:

This plane is responsible for network management and monitoring. It gathers statistics and provides tools for troubleshooting and visibility.

In this case,the control plane provides the routing information and forwarding entries required for the data plane to perform packet forwarding.Therefore, the correct answer isB. Control plane.

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 ondifferent network segmentsand havedifferent subnet masks, one solution is to change the OSPFnetwork typetoPoint-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 isA. Point-to-point.

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 ​.

Comprehensive and Detailed Step-by-Step Explanation:

IPv4 Address Classes:

Class D:Reserved for multicast and defined by the first four bits as1110.

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.

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.

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 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.

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)

Comprehensive and Detailed Step-by-Step Explanation:

1. How Firewalls Match Security Policies:

Firewalls usesecurity policiesto define rules for filtering traffic.

Each policy containsmatching conditions(e.g., source IP, destination IP, protocol, etc.) and anaction(e.g., permit or deny).

Traffic is evaluated against these policies in sequential order, and the first matching policy is applied.

2. Analysis of Each Statement:

Option A: Multiple values can be configured for a single matching condition, and the values are logically ANDed.

Incorrect.

Multiple values for a single matching condition (e.g., multiple source IPs) are logicallyORed, not ANDed. For example, traffic from any of the specified source IPs matches the policy.

Option B: If a security policy contains multiple matching conditions, the relationship between them is AND.

Correct.

When a policy has multiple matching conditions (e.g., source IP AND destination IP AND protocol), all conditions must be met for the policy to match.

Option C: The system has a default security policy named default, where all matching conditions are any and the default action is permit.

Incorrect.

The default security policy typically denies all traffic unless explicitly permitted by user-defined policies.

Option D: When multiple security policy rules are configured, they are sorted in a list by configuration sequence by default. A security policy rule configured earlier is placed higher in the list and has a higher priority.

Correct.

Security policies are processed in sequential order based on their configuration sequence. Policies configured earlier have higher priority and are evaluated first.

3. Summary:

The correct statements areBandD.

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 ​.

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

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 In-Depth Explanation:

STP Port Roles:

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

Designated Port (DP)→Forwards trafficfor a given segment.

RSTP introduces two additional rolesto improve redundancy:

Backup Port→ Aredundant Designated Port(on the same switch).

Alternate Port→ Abackup Root Port(path to the Root Bridge).

Allfour roles exist in RSTP, making the correct answerA, B, C, D.

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

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 > Incompleteis the correct order of priority.

IGMPv1 supports general queries but does not define a Leave message. IGMPv2 introduces the Leave message type, which allows hosts to notify routers when they wish to leave a multicast group, improving efficiency. These distinctions align with the functionality of IGMP versions ​.

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.

 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:

Type 7 LSAs (NSSA External LSAs)are used inNot-So-Stubby Areas (NSSAs)to carry external routing information.

These LSAs aregenerated only by ASBRs within an NSSA, and later converted toType 5 LSAsby theABR.

Stub areas do not allow ASBRs, meaningType 7 LSAs cannot exist in a stub area.

The question incorrectly states thatType 7 LSAs can be generated in stub areas, which isfalse.

????Reference:Huawei HCIA-Datacom Study Guide, OSPF LSA Types and Area Configurations.

The LS age field in OSPF LSAs (Link State Advertisements) is measured in seconds and increments over time in the Link State Database (LSDB). If the LS age reaches the LSRefreshTime (30 minutes), the router that originated the LSA must regenerate it to keep the LSA valid in the network. Options C and B are incorrect since LS age does not decrease, and only the originator regenerates LSAs ​.

In inter-AC roaming scenarios, an AC (Access Controller) can serve as the mobility server for multiple mobility groups, enabling it to manage roaming among multiple groups. However, an AC can only belong to one specific mobility group. This constraint ensures that mobility management remains streamlined and avoids conflicts. Huawei WLAN mobility configuration guides validate this setup ​.

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

AnArea 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), andASBR 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.

 IPv6 Address Behavior

Manually configured link-local addressesdo not have a higher prioritythan automatically generated ones; they coexist and are equally preferred for local communication.

The other statements are true:

A.Link-local addresses can use the EUI-64 method for quick generation.

B.Anycast addresses are only used as destination addresses.

C.An interface can have multiple global unicast addresses with different prefixes.

 HCIP-Datacom-Core Reference

IPv6 address types and priority behaviors are detailed in the IPv6 addressing sections​​.

Comprehensive and Detailed Step-by-Step Explanation:

Bidirectional Forwarding Detection (BFD):

BFD is a lightweight protocol that provides rapid fault detection on links independent of the underlying routing protocol or media.

Requirements for BFD:

Both devices at the endpoints of the link must support and configure BFD for it to operate.

If one device does not support BFD, the feature cannot be used for link detection.

 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​​.

 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 to60 seconds, as per the BGP specification.

 HCIP-Datacom-Core Reference

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

Comprehensive and Detailed Step-by-Step Explanation:

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

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

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

2. Why L2TP Requires Additional Security Measures:

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

To secure L2TP tunnels, it is often paired with IPsec, which provides strong encryption and authentication. The combination of L2TP and IPsec is known asL2TP/IPsec.

3. Why the Statement is TRUE:

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

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.

RPF (Reverse Path Forwarding) checks are used to prevent multicast loops. An RPF check uses theunicast routing table(ormulticast static routes, if configured) to determine the correct incoming interface for a multicast packet.

Multicast protocols like PIM use the RPF mechanism, and the unicast routing table is the primary reference.

Multicast dynamic routing protocolsdo not maintain their own separate tablesfor RPF by default.

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

“RPF checks are performed using the unicast routing table or multicast static routes. The interface through which the multicast source is reachable is considered valid for RPF.”

(Chapter: Multicast – Section: RPF Principle)

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.

Comprehensive and Detailed In-Depth Explanation:

SSH (Secure Shell)providessecure remote loginanddata encryptionover insecure networks.

A. TRUE→ SSH requiresuser authenticationbefore access is granted.

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

C. TRUE→ ACLs can be applied toVTY (Virtual Terminal) linesto restrict SSH access based onIP addresses.

D. FALSE→ The default SSH server port is22, not 23. Port23is used forTelnet, which isless securethan SSH.

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

Comprehensive and Detailed Step-by-Step Explanation:

1. BGP Attributes Overview:

BGP uses attributes to describe the properties of routes. These attributes are classified into the following categories:

Well-Known Mandatory: Attributes that must be recognized and included in every BGP update. Examples: AS_PATH, ORIGIN, NEXT_HOP.

Well-Known Discretionary: Attributes that must be recognized but are not required in every BGP update. Examples: LOCAL_PREF, ATOMIC_AGGREGATE.

Optional Transitive: Attributes that may or may not be recognized, but must be passed along to other BGP peers. Examples: COMMUNITY.

Optional Non-Transitive: Attributes that may or may not be recognized, and are not passed along to other BGP peers. Examples: MED (Multi-Exit Discriminator).

2. Analysis of Each Option:

Option A: Atomic_Aggregate

Correct.

This is a well-known discretionary attribute. It indicates that the advertised route is an aggregate route that summarizes multiple specific routes.

Option B: Local-Preference

Correct.

This is a well-known discretionary attribute. It is used within an AS to prioritize routes, with higher values being preferred.

Option C: Community

Incorrect.

The COMMUNITY attribute is an optional transitive attribute. It is used to tag routes with specific labels to apply routing policies.

Option D: MED (Multi-Exit Discriminator)

Incorrect.

The MED attribute is an optional non-transitive attribute. It is used to influence the choice of the preferred path when there are multiple entry points into an AS.

3. Summary:

Well-Known Discretionary Attributes: Atomic_Aggregate and Local-Preference.

Huawei HCIA-Datacom Study Guide, Chapter "BGP Route Attributes."

RFC 4271: Border Gateway Protocol 4 (BGP-4).

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

To answer this question, it is essential to distinguish between the roles of ABRs and ASBRs in OSPF and the function of route summarization:

Route Summarization on ABRs:

Route summarization in OSPF can reduce the number ofinter-area Type 3 LSAsthat ABRs propagate between areas.

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

Route Summarization on ASBRs:

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

ASBR route summarization does not impactinter-area Type 3 LSAsbecause ASBRs are responsible for importing and summarizingexternal routes, not summarizing routes between OSPF areas.

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

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

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 ​.

 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.

 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​​.

Understanding the Network Setup:

The OSPF network consists of three areas (Area 1, Area 0, and Area 2).

The server's subnet192.168.1.0/24is directly connected to R1 and imported into OSPF using the command:

import-route direct type 1 cost 2

Thetype 1specifies the route as anOSPF Type 1 external route, meaning both the external cost and the internal OSPF cost will be included when calculating the total cost.

The external cost specified for the imported route is2.

Cost Calculation to R2:

The interfaces between the routers are GE interfaces, and the default cost for GE interfaces is1.

The path from R2 to the server goes through the following hops:

R2 → R1:Cost = 1 (intra-area link).

R1 → Server:External cost = 2 (specified in theimport-routecommand).

Total cost to R2:

Intra-area cost (1) + External cost (2) = 3

Verification of Each Option:

Option A (2):Incorrect. This only accounts for the external cost, ignoring the internal OSPF cost.

Option B (4):Incorrect. This overestimates the cost by adding an extra hop.

Option C (3):Correct. The total cost is3(1 for the intra-area link + 2 for the external cost).

Option D (1):Incorrect. This ignores the external cost of the imported route.

 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.

HCIP-Datacom-Core Technology Training Material (OSPF Basics - Router ID and LSA Handling)​.

 Scenario Details:

Different Areas: Even if the two routers belong to different areas, the Router ID remains globally significant in the OSPF domain. This means that any duplication of Router IDs will confuse OSPF mechanisms.

ASBR (Autonomous System Boundary Router): When one of the routers is an ASBR, it generates Type 4 and Type 5 LSAs to describe external routes. These LSAs use the Router ID asan identifier. If another router in the network has the same Router ID, conflicts occur during LSDB synchronization.

TheDHCPNAKmessage is sent by the DHCP server to the client to indicate that the requested configuration is not valid. Messages likeDHCPDiscover,DHCPRequest, andDHCPReleaseare initiated by the client in the DHCP process ​.

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 ​.

 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​​.

 R1 is a Level-1 router in Area 49.0001, while R4 is in Area 49.0004. Level-1 routers only maintain LSDBs for their own area and do not contain LSPs from other areas, such as R4’s LSP.

 R2 is a Level-1-2 router, so it maintains LSDBs for both Area 49.0001 (Level-1) and Level-2 domains, which include LSPs from R4.

 R3 and R4, as Level-2 routers, exchange LSPs with each other within the Level-2 domain.

 Thus, the LSDB of R1 does not include R4’s LSP ​.

Comprehensive and Detailed In-Depth Explanation:

STP (Spanning Tree Protocol) BPDUsdo not contain an explicitport role field. Instead, roles are determined indirectly.

RSTP (Rapid Spanning Tree Protocol)modifies BPDU structureby using theFlags fieldto indicate:

Port roles (Root, Designated, Alternate, Backup)

Proposal/Agreement (P/A) handshake mechanism

The correct field thatspecifies the port role in RSTP BPDUsisFlags.

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

InIPv6, fragmentation is handledonly at the source node. Intermediate routersdo not fragment packets. Instead, if a packet is too large for the next link, the router sends back anICMPv6 Packet Too Bigmessage to the source, which then adjusts its packet size.

This design:

Reduces processing load on intermediate devices.

Supports Path MTU Discovery (PMTUD).

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

“In IPv6, routers do not perform fragmentation. Only the source device fragments packets if needed, based on ICMPv6 feedback.”

(Chapter: IPv6 Fundamentals – Section: Fragmentation and PMTUD)

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.

Thefilter-policycommand in IS-IS is used to control the advertisement and filtering of routing information. However, it does not directly filter LSPs (Link State Packets); instead, it controls route advertisements. The false statement here is that it filters LSPs ​.

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.

The Forwarding Information Base (FIB) is derived from the router's routing table and contains the exact forwarding entries used to route packets. It directly guides packet forwarding decisions by matching incoming packets with the correct output interface or next-hop address ​.

Apseudonodein IS-IS is a logical representation of a broadcast network segment (e.g., Ethernet) where theDesignated Intermediate System (DIS)generates an LSP on behalf of the LAN.

Pseudonode LSPs contain:

Interface information(i.e., the interface that connects to the pseudonode)

Neighbor information(adjacencies with other routers on the LAN)

Protocol information(e.g., supported address families)

However,route information is not containedin LSPs generated by pseudonodes because routing information is advertised in theLSPs generated by the routers themselves, not the pseudonode.

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

“Pseudonode LSPs contain information about the broadcast link, including interface and neighbor data. They do not advertise routing entries.”

(Chapter: IS-IS Advanced Features – Section: DIS and Pseudonodes)

Access Control Lists (ACLs) can be classified into several types, including Basic ACL (filters based on source IP), Advanced ACL (filters based on multiple parameters like source and destination IP, protocol, and ports), and Layer 2 ACL (filters based on MAC addresses). User-defined ACLs are not a standard classification ​.

Comprehensive and Detailed In-Depth Explanation:

ANET (Network Entity Title)consists of three parts:

Area Address→ Identifies the IS-IS area.

System ID→ Uniquely identifies the router.

SEL (NSEL - N-selector)→ Always0in IS-IS.

TheArea Addresspart 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 areB (AFI) and C (IDI).

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

Route summarization in OSPF is restricted to specific routers: Area Border Routers (ABRs) and Autonomous System Boundary Routers (ASBRs). These devices perform summarization to reduce routing table size and minimize advertised routing information between areas or across AS boundaries. Regular routers cannot perform route summarization, making this statement false ​.

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

Comprehensive and Detailed Step-by-Step Explanation:

iMaster NCE-Campus Overview:

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

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

Authentication Modes Supported:

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

Correct Statement:

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

In Huawei firewalls, the security level of a zone can be reconfigured by an administrator, making the statement that it cannot be changed false. Other statements accurately describe security level restrictions or defaults ​.

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.

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

In STP (Spanning Tree Protocol),Bridge Protocol Data Units (BPDUs)contain critical information used in the election and role assignment process, including:

Root Bridge ID– Identifies the current root bridge.

Root Path Cost– Total path cost to reach the root.

Bridge ID– Unique identifier for each switch.These fields are used to determine port roles (root, designated, etc.) and to elect the root bridge.

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

“BPDUs carry the root bridge ID, root path cost, sender’s bridge ID, and port ID. These are used in root bridge election and port role determination.”

(Chapter: Layer 2 Technologies – Section: STP Operation)

All four are valid reasons why IKE (Internet Key Exchange) negotiation might not be triggered:

A– Security policy mismatches canblock data flows, preventing IPsec from initiating.

B– If theroute to the peer is unreachable, no packets can reach the tunnel interface, and IKE will not start.

C– If the IPsec policy is notbound to the correct interface, no protection is triggered.

D– If the ACL doesnot match the actual traffic, the flow will bypass IPsec.

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

“Common causes of IKE negotiation failure include incorrect ACLs, misapplied policies, unreachable peers, and misconfigured security zones.”

(Chapter: VPN Technologies – Section: IPsec Troubleshooting)

Comprehensive and Detailed Step-by-Step Explanation:

Analysis of VRRP Configuration:

Option A (Preemption):Correct. The output explicitly states that preemption is enabled.

Option C (Authentication):Correct. Authentication is enabled using MD5.

Option D (Group ID):Correct. The VRRP group ID is explicitly stated as 1.

False Statement:

Option B (mVRRP Group):The output does not indicate this is anmVRRP (Multicast VRRP)group. This feature must be explicitly configured and is not enabled by default.

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 is128.

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 is128.

Huawei HCIA-Datacom Study Guide, Chapter "RSTP Port Role Election."

IEEE 802.1D-2004: Rapid Spanning Tree Protocol (RSTP).

 Non-Client Definition in IBGP

In an IBGP setup with a Route Reflector (RR), a non-client is an IBGP peer that is neither the RR itself nor its client.

Non-clients must establish fully meshed IBGP connections with all other non-clients and the RR because IBGP rules prohibit route propagation between non-clients without a direct connection.

 HCIP-Datacom-Core Reference

The behavior of non-clients in an RR topology is clearly outlined in the BGP implementation chapters​​.

When the router ID is configured in both the system view and the BGP view, the router ID in the BGP view takes precedence because BGP-specific configurations override global settings. This ensures that BGP operates with the most relevant configurations ​.

Comprehensive and Detailed In-Depth Explanation:

Neighbor Discovery Protocol (NDP)replacesARP in IPv6and usesICMPv6 messagesfor:

Router Solicitation (RS)→ Sent by hosts torequest Router Advertisement (RA) messages.

Router Advertisement (RA)→ Sent by routers to announce prefixes and network parameters.

Neighbor Solicitation (NS)→ Used foraddress resolutionandDuplicate Address Detection (DAD).

Neighbor Advertisement (NA)→ Sent in response toNS messages.

Redirect→ Used by routers toredirect hosts to better gateways.

RS is not directly used for address resolution;Neighbor Solicitation (NS) does this, so the answer should beD.

????Reference:Huawei HCIA-Datacom Study Guide, NDP and ICMPv6 Packet Types.

 IS-IS Interface Types

IS-IS interfaces are categorized based on physical link characteristics:

Point-to-Point (P2P): Direct connections between two routers.

Broadcast: Shared medium networks where multiple routers communicate.

 Incorrect Options

C. P2MP and D. NBMA are not standard interface classifications in IS-IS.

 HCIP-Datacom-Core Reference

IS-IS physical link classifications are elaborated in IS-IS link configuration sections​​.

 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​​.

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.

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 ​.

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 ​.

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 ​.

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 ​.

=========

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)

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

Comprehensive and Detailed In-Depth Explanation:

Type 1 LSAs (Router LSAs)are generated byevery OSPF routerto describe itsdirectly connected linksand their states.

TheRouter ID (RID)must beuniquein an OSPF domain; otherwise, OSPF calculations will fail due toambiguous paths.

If two routersin the same areahave thesame Router ID, OSPF will fail to calculateShortest Path First (SPF)correctly, leading to routing inconsistencies.

To prevent this, Huawei routersautomatically detect duplicate Router IDsand prevent OSPF from functioning properly until the issue is resolved.

????Reference:Huawei HCIA-Datacom Study Guide, Chapter on OSPF LSAs and Router ID Uniqueness.

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 ​.

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 Step-by-Step Explanation:

Default Next Hop Behavior in BGP:

Locally Originated Routes (A):The next hop is set to the advertising router's interface IP address.

Routes Received from EBGP (B):The next hop is not changed when these routes are advertised to IBGP peers. (This makes Option B false.)

Routes Advertised to EBGP (C):The next hop is set to the interface IP address of the advertising router.

Routes Advertised Between IBGP Peers (D):The next hop is not modified by default.

Incorrect Statement:

Option B is incorrect because the next hop of a non-labeled route received from an EBGP peer is not changed when it is advertised to IBGP peers.

Comprehensive and Detailed Step-by-Step Explanation:

1. Understanding Hybrid Interfaces on a Layer 2 Switch:

Layer 2 switches support different interface types, such asaccess,trunk, andhybridinterfaces.

Atrunk interfaceallows traffic from multiple VLANs to pass through, but frames belonging to the native VLAN are sent untagged, while all other VLAN frames are tagged.

Ahybrid interfaceis more flexible:

It allows traffic from multiple VLANs to pass through, just like a trunk interface.

However, you can configure whether frames for specific VLANs are tagged or untagged as they leave the interface. This feature is useful in certain networking scenarios, such as connecting devices that do not support VLAN tagging.

2. Key Differences Between Trunk and Hybrid Interfaces:

A screenshot of a computer Description automatically generated

3. Why the Statement is TRUE:

The statement accurately describes the functionality of a hybrid interface:

It supports traffic from multiple VLANs.

It allows administrators to configure whether outgoing frames are tagged or untagged for specific VLANs.

4. Summary:

The statement isTRUEbecause hybrid interfaces on a Layer 2 switch support traffic from multiple VLANs and allow flexible tagging configurations.

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 alater versionof IGMP is backward-compatible and can identify Report messages from earlier versions.

However, a device running anearlier versionof 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 thesame as or later thanthe 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 In-Depth Explanation:

Wireless LAN (WLAN) roamingallows mobile devices (STAs) to moveseamlessly between different APswithoutdropping connections.

Types of WLAN Roaming:

Layer 2 roaming→ STAs move between APs in thesame subnetwithout IP address changes.

Layer 3 roaming→ STAs move acrossdifferent subnets, requiringIP address reconfiguration(handled via DHCP or tunneling).

Since roamingprevents service interruptionin large WLAN deployments, the statement istrue.

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

Thesilent-interfacecommand 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 ​.

 OSPF Authentication Overview

TheAuth Typefield in the OSPF packet header determines the authentication mode. If theAuth Typeis 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 thatAuth Type = 1corresponds to plaintext​​.

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 isunnecessary 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.

HCIP-Datacom-Core Technology Training Material (BFD Basics and Configuration)​​.

 Mandatory Configurations for Single-Hop BFD:

A. Configure the remote discriminator of a BFD session:The remote discriminator is used to uniquely identify the BFD session at the remote end. This is essential for session establishment.

B. Configure the local discriminator of a BFD session:The local discriminator uniquely identifies the BFD session at the local end. This is required to establish a BFD session.

D. Enable BFD globally:BFD must be enabled globally on the router for the protocol to operate and for session configurations to take effect.

 Optional Configuration:

C. Configure a multicast IP address for BFD:This is not required for single-hop BFD, as it operates over direct links using unicast communication. Multicast is used in other scenarios, like multi-hop BFD.

 Conclusion:The correct configurations for single-hop BFD areA,B, andD.