Free Huawei H12-891_V1.0 Practice Exam with Questions & Answers | Set: 4

According to the displayed OSPF error statistics from the Huawei device, the key HELLO packet error shown is:

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2 : Netmask mismatch

This indicates that the OSPF adjacency formation is failing due to a subnet mask mismatch between the two OSPF neighbors on the corresponding interface (GigabitEthernet 0/0/0). OSPF uses the subnet mask in Hello packets to ensure that neighbors are in the same network. If the masks do not match, OSPF will not form an adjacency.

From the Huawei Official HCIE-Datacom Study Guide (Version 3.0) — under the OSPF Troubleshooting Section:

" Netmask mismatch: If the subnet mask configured on the interfaces of OSPF neighbors does not match, a ' Netmask mismatch ' error occurs. OSPF requires neighbors to be on the same subnet to establish an adjacency. This is a common reason for failure in adjacency formation. "

(Reference: Huawei HCIE-Datacom V3.0, OSPF Troubleshooting Chapter, Section 4.2 – OSPF Hello and Adjacency Establishment Issues)

Thus, among the given options:

A. Area type inconsistency would result in an area ID mismatch error, not netmask.

B. Authentication mismatch would show a bad authentication key or type error.

D. Hello interval mismatches would trigger a Hello timer mismatch error.

Only C. The IP address masks of the interfaces are inconsistent directly matches the actual error observed: Netmask mismatch.

Comprehensive and Detailed Explanation:

✔ SR Policies are dynamically computed and delivered by the SDN controller in an SR-MPLS or SRv6 network.

✔ Correct Statements:

✅ (A) NETCONF is used for delivering configurations like routing policies and service interfaces.

✅ (B) BGP-LS (Link-State) is used to collect topology and compute SR Policies.

✅ (D) BGP IPv6 SR Policy distributes SR policy attributes like color, headend, and endpoints.

✔ Why Is (C) Incorrect?

❌ (C) The controller does not use telemetry to deliver SID entries—telemetry is used for real-time monitoring, not path computation.

???? Reference: Huawei HCIE Datacom – SR Policy and Controller-Based Path Computation

In HTTP status codes:

401 Unauthorized: The server has received the request but requires authentication. This typically means:

No token or credentials were provided.

Credentials/token were incorrect or expired.

Other options:

403 (Access Denied) would mean correct credentials but insufficient permissions.

404: Resource does not exist.

503: Service unavailable.

Correct answer: A. Unauthorized

The command output shows:

* > i before both networks, which means these routes are the preferred routes (*) and are learned via internal BGP (i).

Two networks are listed: 3002::3 and 3002::4, which means R1 does have these two routes in its BGP IPv6 routing table.

For 3002::4, the path origin shows 65001 i, which means this route originated from AS 65001 and was learned through IBGP.

The AS Path attribute is only shown for 3002::4, but both routes are clearly present.

Therefore, the correct conclusion is:

D. R1 has routes 3002::3/128 and 3002::4/128.

Huawei SD-WAN establishes secure tunnels between SD-WAN edge devices (CPEs, AR routers, and controllers) using tunneling protocols.

✅ B. GRE over IPsec (Correct Answer)

GRE (Generic Routing Encapsulation) over IPsec is the primary tunneling method used in Huawei SD-WAN.

GRE provides multi-protocol encapsulation, while IPsec ensures encryption and security.

Used for secure communication over public WAN links (e.g., the internet, LTE, MPLS, etc.).

In YANG model syntax:

cpu-info can be a list node (✓)

cpu-infos can be a container node (✓)

The sampling path does follow the YANG model hierarchy (✓)

However, the prefix huawei-debug: indicates the YANG module name, not an actual data node. Therefore, debug is not necessarily the top node in the YANG hierarchy — it is a node under the huawei-debug namespace/module.

Exact Extract – Huawei Telemetry and YANG Modeling Guide:

“The format < module-name > : < data-node > is used in telemetry to indicate paths. The actual top-level node may differ from the module name.”

Comprehensive and Detailed In-Depth Explanation:

In NETCONF (Network Configuration Protocol), the < config > operation can include operation attributes to specify how configuration data is handled:

merge (B): Merges the new configuration with the existing one.

replace: Replaces the existing configuration with the new one.

create (C): Creates a new configuration node, but will fail if the node already exists.

delete: Deletes an existing configuration node.

remove (A): Removes an existing node, but if the node does not exist, it will not generate an error.

The attribute " update " (D) is not a valid NETCONF operation attribute.

D is the correct answer as it does not exist within the NETCONF operation attribute set.

From the IS-IS error output, the key error is:

Mismatched Area Addr(L1): 13

This clearly indicates that the area addresses are different, which prevents the Level-1 adjacency from forming.

Why is Option D Correct?

IS-IS Level-1 routers must have the same area ID to form an adjacency.

Since the log shows a mismatched area address, the adjacency fails at Level-1.

If R3 and R4 were Level-2 routers, they could form an adjacency even with different area IDs.

Why Are the Other Options Incorrect?

❌ Option A: No authentication failure is reported.

❌ Option B: No " Mismatched Level " errors appear, so their levels are compatible.

❌ Option C: No " Bad Circuit Type " errors indicate mismatched circuit types.

Thus, the correct answer is D.

???? Reference: Huawei HCIE Datacom – IS-IS Neighbor Troubleshooting

There are three standard inter-AS MPLS VPN options, as per RFC 4364:

Option A (Back-to-Back VRF):

VRFs are directly connected between ASBRs using routing exchange (like static/BGP).

No label switching between ASs — no MPLS label needed between ASs.

Option B (EBGP Label Exchange):

ASBRs exchange labeled VPNv4 routes via EBGP.

One MPLS label is required — MPLS forwarding across AS boundary is used.

Option C (End-to-End LSP):

Full end-to-end LSP is created across ASs.

MPLS labels are definitely used end-to-end, even between ASs.

Option D (Commonly vendor-specific extensions based on Option B/C):

Similar to Option C — requires MPLS labels.

So:

B. Option B — needs MPLS label ✅

D. Option D — also needs MPLS label ✅

A. Option A — no MPLS label ❌

C. Option C — also uses MPLS label ✅, but not listed as an answer option in this question format (should have been).

Assuming valid options are A, B, D, the correct ones needing MPLS labels are:

Correct answers: B, D