H12-831_V1.0 Huawei HCIP-Datacom-Advanced Routing & Switching Technology V1.0 Free Practice Exam Questions (2025 Updated)

Comprehensive and Detailed In-Depth Explanation:

Understanding the BGP Network Topology in the Question:

BGP Peering & Route Distribution

Each router forms EBGP peer relationships with directly connected neighbors.

R1 and R4 import the static route 192.168.1.0/24 into BGP and advertise it to their peers.

Community attributes are attached to routes to influence routing policies.

Effect of Community Attribute 1:1

R1 marks 192.168.1.0/24 with community 1:1 before advertising it.

R3 has a policy that rejects any routes with community attribute 1:1.

Since R1’s advertisement contains 1:1, R3 will not accept 192.168.1.0/24 from R2.

Route Selection and Traffic Flow Analysis:

R1 advertises 192.168.1.0/24 with community 1:1 to R2.

R3 rejects this route from R2 because of the configured routing policy.

R4 also advertises 192.168.1.0/24 to its EBGP neighbors without community 1:1.

R5 learns the route from R4 and advertises it to R3.

Since R5’s advertisement does not include community 1:1, R3 accepts the route from R5.

Thus, the best available path for R3 to reach 192.168.1.0/24 is R3 → R5 → R1.

✅ Correct Path: R3 → R5 → R1

Checking Each Option:

❌ Option A: R3 → R2 → R4 (Incorrect)

R3 does not learn the route from R2 because it rejects community 1:1.

Since R1 added 1:1, and R2 propagated the same community, R3 will not accept this path.

❌ Option B: R3 does not have a route to 192.168.1.0/24 (Incorrect)

R3 does have a route, but it learns it from R5 instead of R2.

❌ Option C: R3 → R2 → R1 (Incorrect)

R1 marked the route with 1:1, and R2 advertised it with the same community.

Since R3 rejects 1:1 routes, it will not use this path.

✅ Option D: R3 → R5 → R1 (Correct)

R5 learns the route from R4, which does not have community 1:1, and advertises it to R3.

R3 accepts this route and forwards traffic to R5, which sends it to R1.

Final Conclusion:

✅ D. The correct path for traffic from R3 to 192.168.1.0/24 is R3 → R5 → R1.

Thus, the correct answer is: D.