Huawei H12-821_V1.0 Dumps

Comprehensive and Detailed Step-by-Step Explanation:

1. What is GRE (Generic Routing Encapsulation)?

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

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

2. Analysis of Each Option:

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

Incorrect.

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

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

Incorrect.

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

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

Correct.

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

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

Correct.

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

3. Summary:

The correct options areCandD.

Comprehensive and Detailed Step-by-Step Explanation:

1. Overview of BGP:

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

2. Analysis of Each Option:

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

This statement isincorrect.

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

HCIA-Datacom Study Guide, Chapter "BGP Concepts and Features," Authentication Section.

Option B: BGP uses TCP as the transport layer protocol.

This statement iscorrect.

BGP relies on TCP (Transmission Control Protocol) as its transport layer protocol, specifically on port 179. TCP provides reliable delivery of BGP messages and ensures the session remains established in case of transient network issues.

TCP also handles error recovery and sequencing, making it a suitable choice for BGP, which requires reliable communication between peers.

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 In-Depth Explanation:

SNMP (Simple Network Management Protocol) v3is a moresecureversion of SNMP, supportingauthentication and encryption.

If theNMS is not receiving SNMPv3 traps, possible causes include:

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

B. TRUE→ If theSNMPv3 password is incorrect, authentication will fail, and traps will not be processed by the NMS.

C. FALSE→ The size of packets sent by theNMSdoes not affectincoming SNMP trapsfrom the router.

D. TRUE→ Thecommunity namemust match on both theNMS and the router, or traps will be ignored.

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

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

 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​​.

The virtual MAC address for a VRRP virtual router is determined by the formula00-00-5E-00-01-[VRID in hexadecimal]. For VRID 3, the hexadecimal equivalent is03. Thus, the virtual MAC address is00-00-5E-00-01-03​.

The defaultSTP priorityon Huawei switches (and in the IEEE standard) is32768.

Lower priority values increase the likelihood of a switch becoming the root bridge. You can configure this value in increments of 4096.

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

“The default bridge priority of Huawei switches is 32768. The root bridge is elected based on the lowest bridge ID, which consists of the priority and MAC address.”

(Chapter: Spanning Tree Protocols – Section: RSTP and Bridge Election)

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.

A is false– The correct formula is: Skew_Time = (256 - Priority)/256 × Advertisement_Interval.

B is false– By default, thepreemption delayis typically0s, not 1s, meaning a higher-priority backup router can preempt immediately unless configured otherwise.

C is true– Thedefault Advertisement intervalin VRRP is2 seconds.

D is true– The formula Master_Down_Interval = 3 × Advertisement_Interval + Skew_Time is correct.

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

“The VRRP Skew_Time is calculated as (256 - Priority)/256 × Adver_Interval. The Master_Down interval includes this Skew_Time to stagger failover.”

(Chapter: High Availability – Section: VRRP Timer Mechanism)

The route-policy configuration specifies that node 10 matches the IP prefix11.1.0.0/16and applies a cost of 300 to this route. Once a route matches a node, it is no longer processed by subsequent nodes, making option D incorrect. Option B is also incorrect because only specific matching routes have their costs changed ​.

Comprehensive and Detailed In-Depth Explanation:

BFD (Bidirectional Forwarding Detection)detectslink failuresfaster than traditional mechanisms.

Session states during setup:

AdminDown→ Initial state (session is administratively disabled).

Down→ The session is being established but has not yet exchanged valid control packets.

Init→ The session is partially established (one side has detected the peer).

Up→ The session is fully operational (not part of the setup process).

SinceAdminDown, Down, and Initare involved insession setup, the correct answers areB, C, D.

????Reference:Huawei HCIA-Datacom Study Guide, BFD Session Establishment and States.

Comprehensive and Detailed Step-by-Step Explanation:

Blackhole Route Issue in BGP:

In IBGP, the next hop of a route learned from an EBGP peer is not changed by default. If an IBGP peer cannot reach the next hop, blackhole routes may occur.

To prevent this, thepeer next-hop-localcommand is used to set the next hop to the local router's IP address.

Other Commands:

peer mpls-local-ifnet:Used in MPLS networks to set the next hop as the local interface address.

peer private-nexthop:Allows advertising private IP addresses as the next hop.

peer next-hop-invariable:Ensures the next hop is not modified during route advertisement, which is the opposite of what is required here.

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.

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.

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 toi (IGP).

Option B:Incorrect. Routes learned from EGP have the Origin attribute set toe (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.

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.

 BGP Open Message Components

The Open message contains the following critical parameters:

Local AS Number: The autonomous system of the router.

Router ID: A unique identifier for the router.

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

 Incorrect Option

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

 HCIP-Datacom-Core Reference

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

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​​.

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 ​.

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.

 BGP Route Flapping and Mitigation

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

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

 HCIP-Datacom-Core Reference

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

 ACL Modification

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

Therefore, the statement is incorrect.

 HCIP-Datacom-Core Reference

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

In the provided configuration, IS-IS is enabled onLoopback0but not onLoopback3of R2. As a result, R2 will advertise the route10.0.2.2/32(fromLoopback0) to R1 through IS-IS. However, the route10.0.2.3/32will not be advertised because IS-IS is not enabled on that loopback interface. Theimport-route directcommand does not override this behavior ​.

IS-IS uses a two-level hierarchy:

Level-1 routersoperate within a single area and cannot exchange routing information with routers in other areas directly.

To reach external areas (the IS-IS backbone or other areas), Level-1 routers rely onLevel-1-2 routers, which perform inter-area route redistribution.

Therefore, a Level-1 routermust use a Level-1-2 routeras a gateway to reach destinations outside its own area.

Comprehensive and Detailed In-Depth Explanation:

IP Prefix listsare used tofilter routesbased onprefix and mask length.

Theoptional parametersinclude:

Index of the prefix list→ Specifiespriority/order(Optional).

Shortest mask length to be matched→ Defines theminimum subnet mask(Optional).

Longest mask length to be matched→ Defines themaximum subnet mask(Optional).

Mask length(D) ismandatorybecause it specifies theexact prefix lengthbeing matched.

????Reference:Huawei HCIA-Datacom Study Guide, Configuring Prefix Lists for Route Filtering.

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).

From the command output, the interface S4/0/0 has its cost value explicitly listed under theCostsection as 20 for Level-1 circuits. This means that all traffic routed through this interface will incur this cost in the IS-IS metric calculation. The other options (such as circuit level and IPv6 support) are either not correct or not supported by the provided output ​.

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

Comprehensive and Detailed In-Depth Explanation:

A. TRUE→ Ifpreemption is enabled, ahigher-priority routercan take over as theMaster.

B. TRUE→ Ifpreemption is disabled, thecurrent Master remains activeeven if a higher-priority router joins.

C. TRUE→ TheMaster router sends VRRP Advertisement packetsto maintain its role.

D. FALSE→ If aVRRP router is the IP address owner, itautomatically becomes the Masterwithout needing toparticipate in an election.

????Reference:Huawei HCIA-Datacom Study Guide, VRRP Priority and Preemption Mechanisms.

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) ​.

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 ​.

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:

1. Overview of BFD Optimization:

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

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

2. Analysis of Each Statement:

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

Correct (True Statement).

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

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

Incorrect (False Statement).

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

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

Correct (True Statement).

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

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

Correct (True Statement).

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

3. Summary:

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

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)

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 theApplication Layerof 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.

HCIP-Security Training Material (VPN Basics and SSL VPN Configuration)​​.

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

Comprehensive and Detailed Step-by-Step Explanation:

Portal Authentication:

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

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

Correct Statements:

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

Option D:Portal protocol packets are transmitted overTCPfor reliable communication.

Incorrect Statements:

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

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

On Huawei devices, multiple BGP processes can be configured on the same router, but they are typically used for specific use cases such as multi-instance deployments or virtual routers. This flexibility is supported by Huawei's routing protocols ​.

 GRE Characteristics

GRE doesnotinherently 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​​.

 VRRP and BFD Association:

VRRP (Virtual Router Redundancy Protocol) is used to provide gateway redundancy by electing amasterandbackuprouter.

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.

HCIP-Datacom-Core Technology Training Material (VRRP and BFD Association)​.

 Master_Down_Timer Behavior:

Normally, when a VRRP backup device detects that the master is down (through missed VRRP advertisements), theMaster_Down_Timerdictates the failover timing.

However, when VRRP is associated with BFD:

BFD detects faults immediately (sub-second detection).

The backup device doesnot wait for the Master_Down_Timerto expire. Instead, it immediately assumes the master role upon fault detection by BFD.

An OSPF AS-external LSA is used to describe routes to networks that are external to the OSPF Autonomous System (AS). This external route information is typically imported into OSPF by anAutonomous System Boundary Router (ASBR).

If theForwarding Addressfield in the AS-external LSA is set to 0.0.0.0, this indicates that traffic destined for the external network should be forwarded directly to the ASBR that advertised the external route.

The specific context mentioned here relates to theNot-So-Stubby Area (NSSA), a type of OSPF area designed to handle AS-external routes in a more controlled way. In NSSAs:

Type 7 LSAs are used to describe AS-external routes.

The ASBR within the NSSA converts the Type 7 LSA to a Type 5 LSA before advertising it to the backbone area.

Hence, the correct acronym for the described functionality isNSSA.

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 ​.

 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​​.

Comprehensive and Detailed Step-by-Step Explanation:

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

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

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

2. Resources That VRF Can Independently Own:

Option A: Interface

Correct.

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

Option B: Routing table

Correct.

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

Option C: MAC address table

Incorrect.

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

Option D: Routing protocol process

Correct.

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

3. Summary:

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

Secure access channels include protocols that encrypt the transmitted data to protect against interception or unauthorized access. HTTPS (HyperText Transfer Protocol Secure) ensures data encryption over web communications, while SFTP (Secure File Transfer Protocol) provides secure file transfer by utilizing SSH for data encryption. Telnet and SNMPv2, on the other hand, lack robust encryption and are considered insecure. Huawei security standards highlight the importance of encrypted communication to prevent data leaks ​.

Comprehensive and Detailed In-Depth Explanation:

A. TRUE→ Firewalls maintainsession tableswith adefault session timeout; adjusting it depends onnetwork conditions.

B. FALSE→Fast session aging does not affect persistent connection sessions. Persistent connections (e.g., TCP keepalives)maintain sessionseven if aging settings change.

C. TRUE→ Sessionsmust be constantly matchedwith ongoing traffic to remainactive.

D. TRUE→ Evenwithout stateful inspection, the firewallcreates session entriesfornon-first packetsto maintaincontinuity of services.

????Reference:Huawei HCIA-Datacom Study Guide, Firewall Session Table Mechanism.

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.

A is correct– Confederations arespecifically designed for large-scale BGP deploymentswhere a full IBGP mesh is impractical.

B is correct– Sub-ASs within a confederation establishEBGP-like connectionsbetween each other but behave like IBGP within the overall AS. These sub-ASsdo not require full-mesh inside the confederation, but EBGP rules are followed between sub-ASs.

C is false–Not all devices need to be reconfigured. Devices within the same sub-AS retain normal IBGP behavior and minimal changes.

D is correct– Confederation istransparent to external peers, so thelogical topology remains the samefrom outside the AS.

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

“BGP confederation divides an AS into multiple sub-ASs. EBGP-like sessions are established between sub-ASs, while reducing IBGP mesh complexity. The external AS still sees the AS as one unit.”

(Chapter: BGP Scalability Enhancements – Section: Confederation)

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

 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.

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

Comprehensive and Detailed In-Depth Explanation:

TheFlag fieldin a routing table entry provides specific information about the route.

G (Gateway flag): This flag indicates that the next hop is agateway (another router)rather than a directly connected destination.

S (Static flag): This flag indicates that the route was manually configured as astatic route.

H (Host flag): This flag means that the destination is adirectly connected host, not a network.

D (Dynamic flag): This flag is used fordynamically learned routesfrom protocols like OSPF, EIGRP, or BGP.

Since we are looking for the flag that indicates thenext hop is a gateway, the correct answer isG.

????Reference:Huawei HCIA-Datacom Study Guide, Chapter on Routing Table and FIB Entries.

 ACL Number Ranges

Basic ACLs: Numbered from 2000 to 2999.

Advanced ACLs: Numbered from 3000 to 3999.

Layer 2 ACLs: Numbered from 5000 to 5999.

User-defined ACLs: Numbered from 4000 to 4999.

 HCIP-Datacom-Core Reference

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

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 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.

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 isolateaninternal 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 ​.

Understanding the LSDB and Level-2 DIS Election in IS-IS:

In IS-IS, theDesignated Intermediate System (DIS)is elected for both Level-1 and Level-2 on broadcast networks to manage the link-state database (LSDB) and reduce the number of LSAs exchanged.

The election of the DIS is based on thehighest priority. If the priority is the same, the router with thehighest System IDbecomes the DIS.

HCIP-Datacom-Core Technology Training Material (IS-IS DIS Election)​​.

Analyzing the LSDB:

From the LSDB ofR1, the Level-2 link-state database includes the following entries:

LSPID 0100.0000.3003.00-00: This is R3, and it is present in the Level-2 LSDB with the sequence number and checksum details.

Other routers (R1, R2, R4) are present but do not have the characteristics of the Level-2 DIS in this topology.

Based on the System IDs,R3 (0100.0000.3003)has the highest System ID, making it theLevel-2 DIS.

Conclusion:

The Level-2 DIS on the network isR3, based on the election rules and the LSDB information shown in the figure.

Goal Analysis:

Requirement:

The route to192.168.3.0/24must exist in R1's and R3's routing tables.

The route mustnot exist in R2's routing table.

This requires filtering to ensure the route is either:

Blocked on R2's routing table (via filtering on R2), or

Blocked before it is advertised to R2.

Analysis of Each Option:

Option A (Filter-policy on R2 for filtering received routes):

Applying a filter-policy on R2 to filter received routes will block the route from entering R2's routing table but still allow it to propagate to R3.

This meets the requirement.

Option B (Filter-policy on R2 for filtering the routes to be advertised):

Blocking the advertisement of routes from R2 to other routers does not affect the routes received by R2 itself.

This does not meet the requirement but does not affect the propagation to R3.

This is valid if the received route is blocked.

Option C (Filter-policy on R1 for filtering the routes to be imported):

If the route is filtered on R1 during the import phase, the route will not exist in R1’s routing table and thus cannot be advertised to either R2 or R3.

This fails to meet the requirement because the route must exist in R1's and R3's routing tables.

Option D (Filter-policy on R1 for filtering the imported routes to be advertised):

Filtering routes on R1 before advertising to R2 will prevent R2 from receiving the route but allow R1 to advertise the route to R3.

This meets the requirement.

Correct Option:

C (Filter-policy on R1 for filtering the routes to be imported):This will prevent the route from existing in both R1 and R3, violating the stated requirement.

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 ​.

 MQC and PBR

MQC (Modular QoS Command-Line Interface): Applied to interfaces for classifying and controlling traffic.

PBR (Policy-Based Routing): Used to influence packet forwarding based on policies rather than traditional routing tables.

Both MQC and PBR can be configured on device interfaces to filter incoming/outgoing packets or control their forwarding paths.

 HCIP-Datacom-Core Reference

The use of MQC and PBR on device interfaces is elaborated in the QoS and routing control chapters​​.

In OSPF,Database Description (DD) packetsare used during the database synchronization process. In the first DD packet a router sends during neighbor establishment, three control bits are set:

I bit (Initial)= 1 → This indicates that the DD packet is the first in the sequence.

M bit (More)= 1 → This means more DD packets will follow.

MS bit (Master/Slave)= 1 → Set by the router assuming the master role in the exchange process.

Setting all three bits to 1 is a standard part of the DD exchange initiation.

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

“In the initial DD packet, the I, M, and MS bits are set to 1 by the master router initiating database exchange.”

(Chapter: OSPF Operation Mechanism – Section: Neighbor State Machine)

BGP routes have a variety ofpath attributesthat describe their characteristics and influence route selection. These attributes include well-known mandatory attributes like AS-PATH and NEXT-HOP, as well as optional attributes like MED and LOCAL_PREF.

In Huawei devices, there is aHuawei-specific attributecalled"preference", which is a local parameter used to influence BGP route selection on the device.

Key Characteristics of "preference":

It is valid only locally on the router.

It is not shared with BGP peers.

It helps the router determine the best route when multiple routes exist for the same prefix.

It appears in the BGP routing table output in lowercase aspreference.

Thus, the correct answer ispreference(entered in lowercase as required).

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

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

Open (D):

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

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

Keepalive (A):

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

These messages confirm that the connection is still alive.

Update (C):

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

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

Hello (B):

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

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

 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​​.

Comprehensive and Detailed Step-by-Step Explanation:

HSB (Hot Standby Backup) Service:

HSB is used on WLAN controllers to back up critical information in real time to a backup device, ensuring service continuity in case of failures.

Backed-Up Information:

CAPWAP Tunnel Information (A):Essential for maintaining connections between APs and controllers.

AP Entries (C):Information about connected APs is backed up.

User Data Information (D):Includes client authentication and session details.

Incorrect Option:

DHCP Address Information (B):Not part of HSB's responsibilities, as DHCP is handled separately.

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:

DHCP Configuration Issues:

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

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

Other Options:

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

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

Comprehensive and Detailed Step-by-Step Explanation:

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 ​.

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 ​.

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

Comprehensive and Detailed Step-by-Step Explanation:

Switch Stack Overview:

In a switch stack, roles are assigned asmaster,standby, andslave.

The master handles configuration and control, while the standby serves as the backup master.

Behavior During Master Restart:

D:If the master switch restarts, the standby switch immediately takes over as the new master.

B:After the original master switch restarts, it becomes the master again (default behavior).

Incorrect Options:

A:The slave switch is not promoted to standby before the master switch restart completes.

C:The original standby switch remains the master after the restart.

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.

 OSPF LSA Flooding Mechanism

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

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

 HCIP-Datacom-Core Reference

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

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 ​.

Network Types and Corresponding Link Layer Protocols

Broadcast: Ethernet

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

Point-to-Multipoint (P2MP): PPP

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

 OSPF Network Types:

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

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

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

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

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

Comprehensive and Detailed Step-by-Step Explanation:

Default OSPF Hello Timer:

The OSPF Hello timer is used to send periodic Hello packets and maintain neighbor relationships.

Default Hello timers:

Broadcast and P2P:10 seconds

NBMA and P2MP:30 seconds

Network Types Using 30s Hello Time:

P2MP (C):OSPF sends Hello packets every 30 seconds by default.

NBMA (D):OSPF also uses 30 seconds for NBMA networks.

Inasynchronousmode, the local device sends BFD control packets at predefined intervals, and the remote device monitors the receipt of these packets to detect connectivity issues. This is one of the two operating modes in BFD, the other beingdemandmode ​.

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

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

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

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

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

Comprehensive and Detailed Step-by-Step Explanation:

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.

 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​​.

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

Clarification of the options:

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

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

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

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

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

(Chapter: BGP Path Attributes – Section: AS_Path)

When routes are imported into BGP using theimport-routecommand, the origin attribute is set toincompleteby default. This indicates that the route's origin is not known or is from an external source, as opposed to being explicitly learned through an IGP (IGP) or EGP (EGP) protocol ​.

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.

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

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

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

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

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

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

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

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

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

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

Therefore, the correct answer isD.

The provided BGP error display shows the error timestamp as12:40:39 on March 22, 2010. The error message confirms a mismatch in the peer AS number, as indicated in the "Incorrect remote AS" error info. This eliminates options related to other causes, and the timestamp in Option A is incorrect ​.

 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​​.

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

 Transitive vs. Non-Transitive Attributes

The Community attribute is atransitive 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​​.

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

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

=========

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

OSPF routers establish neighbor relationships and progress through various states during the adjacency formation process. TheExStart stateis where routers negotiate the master and slaveroles. This negotiation is critical because the master initiates the Data Description (DD) packet exchange process.

Here’s a breakdown of the relevant OSPF states:

ExStart State:

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

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

Exchange State:

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

2-way State:

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

Init State:

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

Key Point:

The negotiation of master and slave roles happens exclusively in theExStart state, makingD. ExStartthe correct answer.

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.

BGP does not advertise all routes learned from peers to other peers. By default, only the best (optimal) routes selected by BGP are advertised to other peers. Additionally, routes learned from IBGP peers are not forwarded to other IBGP peers unless a route reflector or confederation setup is used. The statement claiming all learned routes are advertised is false ​.

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

 RST BPDU Handling

On an RSTP network, if a port receives an RST BPDU and determines its own buffered BPDU is superior, it discards the received BPDU without responding. This ensures stability and proper convergence in the network.

 HCIP-Datacom-Core Reference

BPDU handling is described in the RSTP operation chapters​​.