H12-831_V1.0 Exam Questions & Answers

Comprehensive and Detailed In-Depth

This question is based on MPLS (Multiprotocol Label Switching) and its interaction with routing protocols. The goal is to ensure PC1 (10.1.1.1) can communicate with PC2 (10.3.3.1) over MPLS. Let's analyze each option carefully.

1 Understanding MPLS Routing Requirements

To forward traffic using MPLS and LDP, we need:

An IGP (Interior Gateway Protocol) like OSPF or IS-IS to advertise network reachability.

Loopback interfaces advertised in OSPF to establish LDP neighbor relationships.

Consistent MPLS LDP enablement on all links in the MPLS domain.

End-to-end IP reachability between loopbacks (since LDP uses the loopback for label distribution).

2 Option A (Correct Answer) Analysis

This configuration enables OSPF on all routers (R1, R2, and R3) across the MPLS domain:

All networks are advertised in OSPF area 0, ensuring IP reachability. Loopback interfaces (1.1.1.1, 2.2.2.2, 3.3.3.3) are included, which is required for MPLS LDP peer establishment. PC1's network (10.1.1.0/24) and PC2's network (10.3.3.0/24) are properly advertised, ensuring end-to-end connectivity. R1, R2, and R3 have OSPF neighbor relationships, meaning LDP can use OSPF routes for label switching.

Conclusion: Option A meets all MPLS forwarding requirements and is the correct answer.

3 Why Other Options Are Incorrect

Option B (Incorrect)

Uses BGP instead of OSPF, which is not optimal for MPLS forwarding in a simple MPLS domain.

LDP requires an IGP like OSPF or IS-IS to work efficiently.

BGP alone does not establish LDP label bindings between R1, R2, and R3.

Option C (Incorrect)

Mixes OSPF and BGP, causing routing inconsistency.

Uses ip ip-prefix and recursive lookup, which is unnecessary in a standard MPLS domain.

BGP does not distribute labels dynamically like an IGP with LDP.

Option D (Incorrect)

R1 does not advertise the 10.1.1.0/24 network, meaning PC1's network is not reachable.

R3 does not advertise the 10.3.3.0/24 network, meaning PC2's network is not reachable.

Missing essential routing entries for full end-to-end reachability.

HCIP-Datacom Advanced Routing & Switching Technology Huawei Official MPLS and LDP Configuration Guide Huawei Enterprise Networking Documentation

Comprehensive and Detailed In-Depth

To determine the correct answer, we need to analyze how each command impacts OSPF neighbor relationships.

1. Understanding OSPF Neighbor Formation

OSPF routers form neighbor relationships when they meet the following conditions:

They are in the same subnet (IP addresses and subnet masks must match).

They are in the same OSPF area.

They use the same network type (e.g., Broadcast, Point-to-Point).

Authentication (if configured) must match.

Hello and Dead timers must match.

2. Analyzing Each Answer Option

A. 'undo ip address 10.0.12.2 24' Affects OSPF Neighbor Status

Removing the IP address will prevent the interface from sending and receiving OSPF Hello packets.

Without an IP address, OSPF cannot establish neighbor relationships.

Effect: Breaks OSPF neighbor status.

B. 'undo description' Does NOT Affect OSPF Neighbor Status

The interface description is just a label for administrators and has no impact on OSPF functionality.

It does not affect neighbor relationships, routing, or communication.

Effect: No impact on OSPF neighbors.

C. 'undo ospf cost' Affects OSPF Neighbor Status Indirectly

OSPF cost determines the path selection but does NOT break the neighbor relationship.

However, if the cost change leads to routing table recalculations, it might cause temporary convergence issues.

Effect: Does not directly break neighbor status, but affects route selection.

D. 'undo ospf dr-priority' Affects OSPF Neighbor Status (Possibly Causes DR Re-Election)

OSPF DR/BDR election uses priority values.

If changed, a new election might occur, leading to a temporary loss of neighbor relationships.

Effect: Might cause OSPF neighbor reset (temporary impact on adjacency).