Free Practice Questions for Huawei H12-831_V1.0 Exam

Comprehensive and Detailed In-Depth Explanation:

To determine the cost value of the route 10.0.35.0/24 in the routing table of R1, let ' s analyze the possible shortest paths from R1 to R3 (which owns the 10.0.35.0/24 network) based on the given OSPF link costs:

Path 1: R1 → R2 → R3

R1 to R2: Cost = 20

R2 to R3: Cost = 10

Total Cost = 20 + 10 = 30

Path 2: R1 → R4 → R3

R1 to R4: Cost = 10

R4 to R3: Cost = 10

Total Cost = 10 + 10 = 20 ✅ (Lowest cost path)

Path 3: R1 → R5 → R3

R1 to R5: Cost = 10

R5 to R3: Cost = 10

Total Cost = 10 + 10 = 20 ✅ (Equal-cost path)

Final Calculation:

The two best equal-cost paths (R1 → R4 → R3 and R1 → R5 → R3) have a cost of 20.

Since OSPF supports equal-cost multi-path (ECMP) routing and maximum load-balancing 8 is enabled, OSPF will install both routes into the routing table with the same cost of 20.

The path R1 → R2 → R3 has a higher cost (30) and will not be chosen.

Final Answer: ✅ 20 (Option C)

Step 1: Understanding OSPF Areas and Summarization

Area 1 (NSSA - Not So Stubby Area)

Allows external routes but converts Type-5 LSAs into Type-7 LSAs.

External routes must be translated by an ABR into Type-5 LSAs before being propagated into other areas.

Area 2 (Common Area - Regular OSPF Area)

Supports both inter-area and external routes.

asbr-summary 10.0.4.0 255.255.255.0 Command

This command summarizes all external routes within 10.0.4.0/24 into a single summarized route.

Since it is applied on R1 and R3, these routers will advertise 10.0.4.0/24 instead of 10.0.4.4/32 to their respective areas.

Step 2: Route Distribution Analysis

R4 (Originating Router in NSSA - Area 1)

R4 injects 10.0.4.4/32 as a Type-7 LSA into Area 1.

R1 (ABR between Area 1 & Area 0, Summarizing Route)

Since R1 is an ABR, it translates Type-7 LSAs from Area 1 into a summarized Type-5 LSA (10.0.4.0/24) for Area 0.

✅ R1 has 10.0.4.0/24 in its routing table.

R2 (Inside Backbone Area 0, No ASBR Summary Applied Here)

R2 only receives Type-5 LSAs from R1 but does not summarize them.

Since R2 is not explicitly summarizing, it will likely still see 10.0.4.4/32 rather than 10.0.4.0/24.

❌ R2 does not have 10.0.4.0/24.

R3 (ABR between Area 0 & Area 2, Summarizing Route)

R3 is also an ABR and has the asbr-summary 10.0.4.0/24 command configured.

It will advertise the summarized route 10.0.4.0/24 into Area 2.

✅ R3 has 10.0.4.0/24 in its routing table.

R5 (Inside Area 2, No Direct Connectivity to External Routes)

Since R3 summarizes 10.0.4.0/24, R5 (inside Area 2) will receive only summarized routes.

✅ R5 has 10.0.4.0/24.

Final Answer: ✅ R1, R3 (Option A, C)

Comprehensive and Detailed In-Depth Explanation:

To determine the correct configuration, we need to analyze how MPLS LDP (Label Distribution Protocol) is correctly enabled on a Huawei router.

1. Required Steps to Enable MPLS LDP on R1

To enable MPLS LDP on R1 and establish LDP sessions, the following steps must be followed:

✅ Step 1: Configure the MPLS LSR ID (Loopback IP recommended)

MPLS LSR ID is a unique identifier for the Label Switch Router (LSR).

Command:

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mpls lsr-id 1.1.1.1

Why?

The LSR ID must be configured for LDP to function properly in an MPLS network.

It is usually set to a loopback address for stability and consistency.

✅ Step 2: Enable MPLS Globally

Command:

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mpls

Why?

This enables MPLS forwarding on the device.

✅ Step 3: Enable MPLS LDP Globally

Command:

shell

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mpls ldp

Why?

LDP is needed for label distribution in the MPLS domain.

Without this, routers cannot exchange MPLS labels.

✅ Step 4: Enable MPLS and LDP on the Required Interface

Command:

shell

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interface gigabitethernet 0/0/1

mpls

mpls ldp

Why?

MPLS must be enabled on interfaces that participate in MPLS forwarding.

LDP must also be enabled on these interfaces to distribute labels over MPLS links.

2. Analyzing the Answer Choices

✅ Option B (Correct)

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[R1] mpls lsr-id 1.1.1.1 ✅ (Sets LSR ID)

[R1] mpls ✅ (Enables MPLS globally)

[R1-mpls] quit

[R1] mpls ldp ✅ (Enables LDP globally)

[R1-mpls-ldp] quit

[R1] interface gigabitethernet 0/0/1

[R1-GigabitEthernet0/0/1] mpls ✅ (Enables MPLS on interface)

[R1-GigabitEthernet0/0/1] mpls ldp ✅ (Enables LDP on interface)

[R1-GigabitEthernet0/0/1] quit

This configuration correctly enables MPLS LDP on R1.

All required steps are followed, including the LSR ID, MPLS, LDP, and interface activation.

❌ Option A (Incorrect)

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[R1] mpls lsr-id 1.1.1.1

[R1] mpls

[R1-mpls] quit

[R1] mpls ldp

[R1-mpls-ldp] quit

[R1] interface gigabitethernet 0/0/1

[R1-GigabitEthernet0/0/1] mpls ✅

[R1-GigabitEthernet0/0/1] quit ❌ (Missing " mpls ldp " under interface)

Missing mpls ldp under interface configuration.

Without this, the interface will not establish an LDP session → Incorrect.

❌ Option C (Incorrect)

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[R1] mpls

[R1-mpls] quit

[R1] mpls ldp

[R1-mpls-ldp] quit

[R1] interface gigabitethernet 0/0/1

[R1-GigabitEthernet0/0/1] mpls

[R1-GigabitEthernet0/0/1] mpls ldp

[R1-GigabitEthernet0/0/1] quit

Missing mpls lsr-id 1.1.1.1.

LSR ID is critical for LDP sessions → Incorrect.

❌ Option D (Incorrect)

shell

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[R1] mpls lsr-id 1.1.1.1

[R1] mpls

[R1-mpls] quit

[R1] interface gigabitethernet 0/0/1

[R1-GigabitEthernet0/0/1] mpls

[R1-GigabitEthernet0/0/1] mpls ldp

[R1-GigabitEthernet0/0/1] quit

Missing global MPLS LDP configuration (mpls ldp).

Without enabling LDP globally, labels will not be distributed.

This makes LDP sessions fail. → Incorrect.

Although BGP supports load balancing across multiple equal-cost routes, configuring a maximum of eight routes does not guarantee that eight routes will become active.

Huawei BGP compares several attributes when determining whether multiple routes qualify for ECMP forwarding. These include PrefVal, Local_Pref, AS_PATH, Origin, MED, and other applicable route-selection attributes.

In the topology, R3 receives advertisements for 192.168.1.0/24 through different autonomous systems. Consequently, the received routes contain different AS_PATH attributes.

By default, Huawei BGP requires matching AS_PATH attributes for ordinary load balancing. Paths with different AS sequences do not qualify merely because their AS_PATH lengths are equal.

No load-balancing as-path-ignore configuration is specified in the question.

Therefore, R3 selects one best BGP route, even though the configured maximum is eight. The correct answer is C.

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1. Understanding VLAN Aggregation in Huawei Switches

VLAN aggregation is a technique that groups multiple VLANs (sub-VLANs) under a single Super-VLAN.

Super-VLANs do not have member interfaces but include multiple Sub-VLANs that share a common gateway (VLANIF interface).

2. Inter-Sub-VLAN Communication Requirement

By default, hosts in different sub-VLANs cannot communicate directly.

To enable communication between different sub-VLANs within the same Super-VLAN, an inter-sub-VLAN proxy must be enabled.

This is done using the inter-sub-vlan-proxy enable command in the VLANIF interface of the Super-VLAN.

3. Correct Command Usage

The command format is:

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supervlan inter-sub-vlan-proxy enable

This command must be executed under VLANIF 10, corresponding to the Super-VLAN.

4. Why is the Answer " supervlan " ?

The missing parameter in the command should be supervlan, because it is used to enable communication between Sub-VLANs under a Super-VLAN.

This is a specific Huawei command used in HCIP-Datacom-Advanced Routing & Switching Technology certification.

Comprehensive and Detailed In-Depth Explanation:

To verify the correct answers, let ' s analyze how BGP/MPLS IP VPN is used for secure communication and isolation in an enterprise network.

1. Understanding BGP/MPLS IP VPN Concepts

MPLS VPN (Multiprotocol Label Switching Virtual Private Network) is used to:

Allow communication between specific sites by using Route Targets (RTs).

Ensure isolation of specific areas (e.g., R & D vs. non-R & D) by controlling RT import/export policies.

Utilize Route Distinguisher (RD) to make overlapping IP addresses unique within the VPN.

2. Analyzing the Answer Choices

✅ A. " To enable communication between the headquarters and branch R & D areas, both the ERT and IRT of VPN1 and VPN2 can be set to 100:100. " → TRUE

Explanation:

ERT (Export Route Target) and IRT (Import Route Target) define which VPNs share routing information.

If VPN1 (HQ R & D) and VPN2 (Branch R & D) use the same RT (100:100), they will exchange routes, enabling communication.

Correct configuration:

VPN1: ERT 100:100, IRT 100:100

VPN2: ERT 100:100, IRT 100:100

✅ This is correct and enables communication between HQ and branch R & D areas.

❌ B. " To implement communication between the headquarters and branch R & D areas, the RDs of VPN1 and VPN2 need to be set to the same value. " → FALSE

Explanation:

RD (Route Distinguisher) is only used to make overlapping IP addresses unique within the MPLS VPN.

RD does NOT control route exchange between VPNs (RTs control route exchange).

VPN1 and VPN2 can have different RDs but still communicate if they share the same RT (100:100).

✅ RDs do NOT need to be the same for VPNs to communicate.

❌ This statement is false.

❌ C. " R & D areas and non-R & D areas have overlapping address spaces. Therefore, services in the two areas cannot be isolated. " → FALSE

Explanation:

Overlapping address spaces are common in MPLS VPNs and can be isolated using unique Route Targets (RTs).

As long as VPNs have different RTs, their traffic remains isolated.

For example:

VPN1 (R & D): RT 100:100

VPN3 (non-R & D): RT 200:200

Even with overlapping IPs, R & D and non-R & D areas are completely isolated.

❌ This statement is false.

✅ D. " To isolate R & D areas from non-R & D areas at the headquarters, the RTs of VPN1 can all be set to 100:100 and the RTs of VPN3 can all be set to 200:200. " → TRUE

Explanation:

Setting different RTs for R & D (100:100) and non-R & D (200:200) ensures complete isolation.

Correct configuration:

VPN1 (R & D): RT 100:100

VPN3 (non-R & D): RT 200:200

Since VPN1 and VPN3 do NOT share the same RTs, their routes remain separate.

✅ This ensures isolation between R & D and non-R & D areas.

This statement is false. In Huawei ' s implementation of OSPF equal-cost load balancing, when multiple candidate routes have equal metrics and the number of routes exceeds the configured maximum load-balancing limit, the selection order is:

Interface priority (higher is preferred)

Interface index (smaller is preferred)

Next-hop IP address (smaller is preferred if others are the same)

So, smaller interface indexes are preferred—not larger.

✅ Official Reference from Huawei:

" If the number of equal-cost routes exceeds the maximum supported number, the device selects preferred routes in the following order: interface priority, interface index (smaller preferred), and next-hop IP address. "

— [Huawei HCIA-Datacom Certification Guide – OSPF Chapter]

When OSPF detects a failure in the network, it performs a series of actions to ensure traffic is rerouted to a valid path. The phases occur in this strict order:

✅ Fault Detection (A)

OSPF routers use Hello packets to maintain neighbor relationships.

If a Hello timeout or link down is detected, the fault is immediately recognized.

✅ LSA Update (B)

Upon detecting a failure, the router generates a new LSA (e.g., a Router-LSA or Network-LSA) and floods it to all other routers in the same area.

This LSA communicates the change in network topology.

✅ Route Calculation (C)

Each router that receives the updated LSAs runs the SPF algorithm to recompute the best path to every destination.

✅ Entry Delivery to the FIB (D)

After recalculating the routes, the router installs the new forwarding entries into the FIB (Forwarding Information Base), allowing data to be forwarded along the new optimal path.

✅ Official Huawei Reference:

" OSPF convergence after a network failure consists of fault detection, LSA flooding, SPF calculation, and updating the FIB. Each step must be completed for traffic to resume correctly on alternate paths. "

— [Huawei HCIA-Datacom Certification Guide – Chapter: OSPF Convergence and SPF Algorithm]