Pass the Huawei HCIP-Datacom H12-831_V1.0 Questions and answers with CertsForce

Comprehensive and Detailed In-Depth Explanation:

Understanding the IS-IS Network Structure in the Question:

IS-IS Area IDs and Router Roles

Area 49.0001 (Level-1-2): Contains R1, R2, R4 (all Level-1-2 routers).

Area 49.0002 (Level-1-2 & Level-1): Contains R3 (Level-1-2) and R5 (Level-1 only).

Key Command Used: ipv6 default-route-advertise always level-1

This command forces R4 to advertise a default route (::/0) to all Level-1 routers within its area.

Only Level-1 routers in the same area as R4 will receive the default route.

Level-2 routers do not receive or propagate this default route unless additional configuration is done.

Route Distribution Analysis:

R4 (Level-1-2) is configured to advertise a default route to Level-1 routers.

R1 and R2 (both Level-1-2) are in the same area (49.0001) as R4, so they receive the default route.

R3 (Level-1-2) is in area 49.0002 but connects to R4 (49.0001), meaning it can receive the default route through its Level-1 connection.

R5 (Level-1 only) is in area 49.0002, but R4 does not propagate the default route to another Level-1 area (49.0002).

Since R5 is a Level-1 router and does not have a Level-2 connection, it cannot receive the default route from R4.

Final Conclusion:

✅ R1 receives the default route.✅ R2 receives the default route.✅ R3 receives the default route.❌ R5 does NOT receive the default route.

Thus, the correct answer is: C. R5.

Comprehensive and Detailed In-Depth Explanation:

OSPF Hello packets are used to establish and maintain neighbor relationships between routers.

Hello packets contain:✅ Router ID – Unique identifier for the OSPF router.✅ Area ID – Defines the OSPF area to which the router belongs.✅ Network Mask – Helps ensure routers are on the same subnet.

Process ID is NOT included because the OSPF Process ID is a local parameter used only within the router itself and is not exchanged between routers.

???? Reference: HCIP-Datacom Advanced Routing & Switching Technology – OSPF Packet Types

Comprehensive and Detailed In-Depth Explanation:To determine whether the statement is true or false, we need to analyze the OSPFv3 topology, the role of area types, and the behavior of Inter-Area-Prefix-LSAs. Let’s break it down step by step:

Understanding the OSPFv3 Topology and Area Types:

The figure shows three routers (R1, R2, and R3) connected in an OSPFv3 network. R1 and R2 are in Area 0 (the backbone area), while R2 and R3 are in Area 1 (a common area, also known as a standard or regular area).

R2 is an Area Border Router (ABR) because it connects Area 0 and Area 1. ABRs are responsible for summarizing and advertising routes between areas.

What is a Common Area in OSPFv3?:

A "common area" in OSPFv3 refers to a standard or regular OSPF area, as opposed to special areas like Stub, Totally Stubby, Not-So-Stubby Area (NSSA), or Totally NSSA. Common areas allow all types of LSAs, including inter-area, intra-area, and external LSAs, to be flooded within the area, except for restrictions in special area types.

Since Area 1 is described as a "common area," it behaves like a standard OSPF area, allowing the full exchange of LSAs, including Inter-Area-Prefix-LSAs.

Role of Inter-Area-Prefix-LSA (Type 3 LSA in OSPFv3):

Inter-Area-Prefix-LSAs (Type 3 LSAs in OSPFv3) are used by ABRs to advertise prefixes from one area to another. These LSAs are critical for inter-area routing, allowing routers in one area to learn about networks in other areas.

In this case, R2, as an ABR, generates Inter-Area-Prefix-LSAs to describe routes (network segments) in Area 1 and advertises them into Area 0. Conversely, R2 also receives Inter-Area-Prefix-LSAs from Area 0 (via R1) and advertises them into Area 1.

Does the Inter-Area-Prefix-LSA Exist in Both Area 0 and Area 1?:

Yes, Inter-Area-Prefix-LSAs exist in both areas because R2, as an ABR, floods these LSAs into both Area 0 and Area 1. Specifically:

R2 generates Inter-Area-Prefix-LSAs for network segments in Area 1 and advertises them into Area 0, where R1 (in Area 0) can receive and process them.

Similarly, R2 receives Inter-Area-Prefix-LSAs for network segments in Area 0 (from R1) and advertises them into Area 1, where R3 (in Area 1) can receive and process them.

Since Area 1 is a common area (not a stub or NSSA), it allows Inter-Area-Prefix-LSAs to be flooded within the area, ensuring that routers like R3 can learn about routes in Area 0, and routers like R1 can learn about routes in Area 1.

Verifying the Statement:

The statement claims that R2 generates an Inter-Area-Prefix-LSA to describe the routes of a network segment in Area 1, and such an LSA exists in both Area 0 and Area 1. This is accurate because:

R2, as an ABR, generates Inter-Area-Prefix-LSAs for Area 1’s network segments and floods them into Area 0.

R2 also receives and floods Inter-Area-Prefix-LSAs from Area 0 into Area 1.

Therefore, Inter-Area-Prefix-LSAs describing routes in Area 1 exist in both Area 0 and Area 1, making the statement true.

Conclusion:

The statement is true because Inter-Area-Prefix-LSAs generated by R2 for Area 1’s network segments are flooded into both Area 0 and Area 1, and Area 1, being a common area, allows these LSAs to exist within it.

References to HCIP-Datacom-Advanced Routing & Switching Technology Documents:

HCIP-Datacom-Advanced Routing & Switching Technology V1.0, Section on OSPFv3: OSPF Area Types, Inter-Area Routing, and LSA Types (specifically Inter-Area-Prefix-LSA, Type 3 LSA).

HCIP-Datacom-Advanced Routing & Switching Technology V1.0, Chapter on OSPF Routing Protocols: ABR Behavior, Common Areas, and LSA Flooding Mechanisms.

Comprehensive and Detailed In-Depth Explanation:

Step 1: Identify the Primary Path

The shortest OSPF cost to 10.0.3.3/32 from R1 is through R5:

R1 → R5 (Cost 10) → R3 (Cost 10) = Total Cost 20

The primary outbound interface from R1 to R5 is GE0/0/1.

Step 2: Identify the Backup Path (OSPF IP FRR & ECMP)

OSPF IP Fast Reroute (FRR) provides a backup next-hop in case the primary link (R1 → R5) fails.

A feasible backup path must have a cost equal to or close to the primary path, but it must avoid the same failure point.

Alternative Path Calculation:

Path 1 (R1 → R2 → R3)

R1 → R2 (Cost 10), R2 → R3 (Cost 10) → Total Cost = 20 ✅

Uses interface GE0/0/2 on R1.

Path 2 (R1 → R4 → R3)

R1 → R4 (Cost 10), R4 → R3 (Cost 10) → Total Cost = 20 ✅

Uses interface GE0/0/3 on R1.

Final Decision on the Backup Interface

Since both paths R1 → R2 → R3 and R1 → R4 → R3 have equal costs, either can be used for backup.

However, R1 → R2 → R3 shares a direct cost path with R5, meaning it may not be preferred as a full FRR backup.

The best backup outbound interface in this scenario is GE0/0/3 (R1 → R4 → R3).

Final Answer: ✅ C (GE0/0/3)

References:

HCIP-Datacom-Advanced Routing & Switching Technology V1.0 – OSPF IP FRR (Fast Reroute) Mechanism

OSPF Equal-Cost Multi-Path (ECMP) and Backup Route Selection

OSPF Route Calculation and Best-Path Selection