Huawei H12-831_V1.0 Exam - Topic 8 Question 72 Discussion

Actual exam question for Huawei's H12-831_V1.0 exam

Question #: 72
Topic #: 8

On the network shown in the figure, EBGP peer relationships are established between ASs through directly connected interfaces.

OSPF is deployed in AS 65456 (with OSPF disabled on interconnected interfaces between ASs).

R4 and R5 use Loopback0 to establish iBGP peer relationships with R6.

The IP address of Loopback0 on each router is 10.0.X.X/32, and the router ID is 10.0.X.X, where X is the number of the router.

R1, R2, and R3 import the external route 192.168.1.0/24 into BGP through the import-route command.

Which of the following statements are true?

A. For 192.168.1.0/24, R5 preferentially selects the route received from R2. B. For 192.168.1.0/24, R4 preferentially selects the route received from R1. C. For 192.168.1.0/24, if the default local-preference 150 command is configured on R3, R5 preferentially selects the route received from R3. D. For 192.168.1.0/24, R6 preferentially selects the route received from R4.

AFor 192.168.1.0/24, R5 preferentially selects the route received from R2. (Correct)
R5 is in AS 65456 and peers with R6 using iBGP.
Since R2 is a central router with direct connectivity to R5, it is the most preferred path compared to indirect paths from R1 or R3.
By default, R5 will prefer the path from R2 over others unless explicitly influenced by BGP attributes.
Statement A is correct.

BFor 192.168.1.0/24, R4 preferentially selects the route received from R1. (Incorrect)
R4 and R5 use Loopback0 to establish iBGP with R6, meaning they receive BGP routes from multiple sources.
BGP prefers the shortest AS path, and there is no specific information indicating that R1's path is the shortest for R4.
R4 may actually prefer another router's advertisement (e.g., R2 or R3) depending on AS path length and other attributes.
Statement B is incorrect.

CFor 192.168.1.0/24, if the default local-preference 150 command is configured on R3, R5 preferentially selects the route received from R3. (Correct)
By default, BGP assigns a local-preference of 100.
If R3 sets local-preference to 150, it is higher than other routes (R1, R2).
BGP prefers the highest local-preference value, so R5 will prefer the route received from R3 if this attribute is set.
Statement C is correct.

DFor 192.168.1.0/24, R6 preferentially selects the route received from R4. (Incorrect)
R6 is an iBGP peer of both R4 and R5.
BGP best-path selection depends on attributes like local-preference, AS-path, and MED.
There is no explicit information suggesting that R4's advertisement is preferred over R5's.
R6 may prefer R5's route depending on attributes.
Statement D is incorrect.
Final Conclusion:
A. R5 preferentially selects the route received from R2.
B. R4 does not necessarily prefer R1's route.
C. If R3 sets local-preference 150, R5 will prefer the route from R3.
D. R6 does not necessarily prefer R4's route.
Thus, the correct answers are: A, C.

Show Suggested Answer

Suggested Answer: A, C

Comprehensive and Detailed In-Depth

Understanding the BGP and OSPF Network Topology in the Questio n :

External Route Importation

R1, R2, and R3 import 192.168.1.0/24 into BGP from an external source.

This means R1, R2, and R3 will advertise this route to their EBGP and iBGP peers.

BGP Route Selection Criteria

BGP follows specific rules to determine the best path for a route. The most relevant factors here are:

Highest Local Preference (LOCAL_PREF) Preferred

Shortest AS Path Preferred

Lowest Origin Type (IGP < EGP < Incomplete) Preferred

Lowest MED (Multi-Exit Discriminator) Preferred

Oldest eBGP route (if paths are equal) Preferred

Route Selection Analysis for Each Statement:

HCIP-Datacom-Advanced Routing & Switching Technology V1.0 -- BGP Route Selection and Local Preference

Huawei Official HCIP-Datacom Study Guide -- BGP iBGP Peering and Best Path Selection Rules

Huawei Documentation on BGP Local-Preference and Route Selection Behavior

by Lilli at Jul 11, 2025, 05:45 AM

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7 months ago

Haha, local-preference 150 on R3? That's a bold move. I bet the exam writers are trying to trip us up with that one.

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Goldie

5 months ago

I agree, it's a tricky move but can influence BGP path selection.

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Allene

7 months ago

Yeah, setting local-preference to 150 can definitely change the route selection.

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Junita

7 months ago

Wow, this BGP stuff is complex. I'm just glad I don't have to configure it myself. Imagine getting these tricky questions wrong on the exam!

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7 months ago

I think R5 prefers the route from R2.

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