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

Comprehensive and Detailed In-Depth Explanation:

MPLS packet forwarding is based on label information stored in the LFIB (Label Forwarding Information Base).

The role of different tables in MPLS:✅ RIB (Routing Information Base): Stores routing information, but does not handle MPLS label forwarding.✅ LIB (Label Information Base): Stores label bindings but is used for control-plane operations.✅ FIB (Forwarding Information Base): Used for IP forwarding, not MPLS forwarding.✅ LFIB (Label Forwarding Information Base): The correct table, which maps incoming labels to outgoing labels (or actions like swap, push, pop) and is used for actual MPLS packet forwarding.

???? Reference: HCIP-Datacom Advanced Routing & Switching Technology – MPLS LFIB and Label Forwarding

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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This statement is false. Time zone configuration using the clock timezone command affects only the local display of time on a device (e.g., logs, timestamps), and has no effect on dynamic routing protocol operation.

OSPF, BGP, IS-IS, and other routing protocols do not rely on time synchronization or time zone matching between devices to establish neighbor relationships.

Even if devices are in different time zones, they can still form adjacencies as long as IP connectivity and protocol parameters (e.g., hello/dead intervals, authentication) are correctly configured.

✅ Official Reference from Huawei:

" The clock timezone command sets the local time zone for display purposes. It does not affect protocol operations or neighbor relationships. "

— [Huawei HCIA-Datacom Certification Guide – System Management Section]

Comprehensive and Detailed In-Depth Explanation:

Understanding DHCP Snooping and Trusted/Untrusted Ports

1. What is DHCP Snooping?

DHCP Snooping is a security feature that prevents rogue DHCP servers from providing unauthorized IP configurations to clients.

It categorizes switch ports into:

Trusted Ports: Allow DHCP Offer and ACK messages from a legitimate DHCP server.

Untrusted Ports: Block unauthorized DHCP responses to prevent rogue DHCP attacks.

Analyzing the Network Setup in the Figure

Interface

Connected Device

DHCP Role

Should it be Trusted?

GE0/0/1

PC1 (DHCP Client)

Requests DHCP leases

❌ Untrusted

GE0/0/2

DHCP Server (Legitimate)

Provides DHCP leases

✅ Trusted

GE0/0/3

Web Server

Not involved in DHCP

❌ Untrusted

GE0/0/4

Bogus (Rogue) DHCP Server

Malicious DHCP Server

❌ Untrusted & Blocked

GE0/0/2 is connected to the legitimate DHCP server, meaning it should be marked as a TRUSTED interface.

GE0/0/4 connects to a bogus DHCP server, which must be UNTRUSTED to block unauthorized DHCP responses.

GE0/0/1 (Client) and GE0/0/3 (Web Server) do not need to be trusted.

✅ Thus, the correct answer is: D. GE0/0/2.

Final Conclusion:

✅ GE0/0/2 should be configured as the trusted DHCP interface.

❌ GE0/0/1 (Client) should remain untrusted.

❌ GE0/0/3 (Web Server) does not need DHCP trust.

❌ GE0/0/4 (Bogus DHCP Server) should be blocked.

Thus, the correct answer is: D. GE0/0/2.

Comprehensive and Detailed In-Depth Explanation:

1. Understanding MPLS LDP (Label Distribution Protocol)

LDP (Label Distribution Protocol) runs over TCP port 646.

LDP uses the transport address (Loopback0 in this case) to establish TCP sessions between neighbors.

For an LDP session to be established, both routers must:

Enable LDP on the interface (GE0/0/1).

Allow TCP traffic on port 646 (used for LDP adjacency formation).

2. Analyzing the Issue and Possible Causes

The figure shows a successful ping from R2 to R1’s Loopback0 (10.0.1.1/32).

This means basic IP connectivity between R1 and R2 is working.

OSPF is properly advertising Loopback0 addresses between the routers.

The problem must be related to LDP itself, not general IP reachability.

3. Evaluating Each Answer Option

Option A: " R1’s GE0/0/1 rejects packets with the destination IP address 10.0.2.2. "

Incorrect.

The ping test in the figure shows successful replies from 10.0.1.1 to 10.0.2.2, meaning packets to 10.0.2.2 are not being rejected.

This is NOT the cause of the LDP failure.

Option B: " MPLS LDP is not enabled on R2’s GE0/0/1. "

Correct.

If LDP is not enabled on R2’s GE0/0/1, then R1 and R2 cannot form an LDP session.

MPLS LDP must be enabled on both interfaces for label exchange.

This is a valid cause of the issue.

Option C: " R2’s GE0/0/1 rejects packets with TCP destination port 646. "

Correct.

LDP operates over TCP port 646, so if R2’s GE0/0/1 has a firewall or ACL blocking TCP port 646, then LDP will fail.

Blocking TCP 646 on R2’s interface would prevent the session from establishing.

This is another valid cause of the issue.

Option D: " R1’s GE0/0/1 rejects packets with UDP destination port 646. "

Incorrect.

LDP does not use UDP; it uses TCP port 646.

This is not a valid cause of the issue.

Final Answer:

✅ B and C are correct.

HCIP-Datacom-Advanced Routing & Switching Technology References:

MPLS LDP Session Establishment and TCP 646 Dependency

How OSPF Advertises Loopback0 for LDP Transport

Common LDP Debugging Techniques and ACL Issues

PIM Sparse Mode (PIM-SM) elects a Designated Router (DR) on a shared network segment to coordinate multicast source registration and receiver-side multicast forwarding.

The election first compares the DR priorities advertised in PIM Hello messages.

The router with the highest DR priority is selected. When routers have equal priorities, the router with the numerically highest interface IP address wins.

In the topology, R1 uses 10.0.12.1/24 and R2 uses 10.0.12.2/24. Both routers use default DR priority values.

Because 10.0.12.2 is higher than 10.0.12.1, R2 is elected as the PIM-SM Designated Router.

This differs from the IGMPv2 querier election, which selects the router with the lowest IP address. Thus, R1 would be the IGMP querier, but R2 is the PIM-SM DR.

Comprehensive and Detailed In-Depth Explanation:

OSPFv3 (for IPv6) packets are directly encapsulated in IPv6 without using UDP or TCP.

The Next Header field in IPv6 is similar to the Protocol field in IPv4, indicating the protocol type of the payload.

IANA (Internet Assigned Numbers Authority) has assigned protocol number 89 to OSPF.

OSPFv3 packets always use Next Header value = 89 inside IPv6 headers.

???? Reference: HCIP-Datacom Advanced Routing & Switching Technology – OSPFv3 Packet Encapsulation

A = 50

B = 10

C = 20

Comprehensive and Detailed In-Depth Explanation:

Understanding OSPF Path Selection and Cost Calculation:

OSPF selects the shortest path (lowest cost) to the destination.

The OSPF cost is determined by the cumulative sum of interface costs along a path.

By assigning specific costs to A, B, and C, we can influence OSPF’s path selection to meet the desired routing behavior.

Step-by-Step Analysis of Required Traffic Flow:

1. Traffic from PC1 to PC2 must take the route:

PC1 - > R1 - > R3 - > R2 - > PC2

To force traffic through R3, the cost of the direct link R1 - > R2 (Cost-A) must be higher than the alternative path via R3.

We assign Cost-A = 50 (high cost) to discourage direct routing from R1 - > R2.

The cost of R1 - > R3 (Cost-C) should be lower, so we assign Cost-C = 20.

The cost of R3 - > R2 (default Cost-20) remains unchanged.

Total cost via R3: 20 (R1- > R3) + 20 (R3- > R2) = 40, which is less than the direct link of 50, so OSPF prefers this path.

✅ Traffic follows: PC1 - > R1 - > R3 - > R2 - > PC2

2. Traffic from PC2 to PC1 must take the route:

PC2 - > R2 - > R1 - > PC1

We need to make R2 - > R1 (Cost-B) the best (lowest cost) route for return traffic.

Assign Cost-B = 10 (low cost).

This ensures that R2 prefers the direct path R2 - > R1 instead of R2 - > R3 - > R1 (which costs 20+20=40).

✅ Traffic follows: PC2 - > R2 - > R1 - > PC1

Final Cost Assignments for Correct Routing Behavior:

Cost

Assigned Value

Reason

Cost-A (R1 - > R2)

50

High to discourage direct R1- > R2 routing

Cost-B (R2 - > R1)

10

Low to ensure PC2- > PC1 prefers direct R2- > R1

Cost-C (R1 - > R3)

20

Medium to encourage R1- > R3- > R2 path

Key Takeaways:

Higher OSPF cost discourages path selection.

Lower OSPF cost encourages path selection.

By manipulating OSPF cost values, we achieve asymmetric routing between PC1 and PC2.

This aligns with OSPF path selection principles covered in HCIP-Datacom certification.

HCIP-Datacom-Advanced Routing & Switching Technology References:

Huawei HCIP-Datacom Official Certification Guide, Chapter on OSPF Cost Calculation and Path Selection.

Huawei Enterprise Networking Training Materials, OSPF Path Optimization Techniques.

Huawei Datacom Configuration Guide, OSPF Cost and Traffic Engineering.