Pass the Huawei HCIE-Datacom H12-891_V1.0 Questions and answers with Dumpstech

Why is Free Mobility Not Based on VLANs or IP Addresses?

Free mobility in Huawei CloudCampus implements policy-based user access control based on user identity (rather than VLANs or IP addresses).

Users can move across different network locations while maintaining their assigned security and access policies.

✅ How Free Mobility Works:

Policies are applied based on User Groups instead of VLAN or IP.

Uses Group-Based Policy Control (GBP) and Software-Defined Access (SDA) principles.

❌ Incorrect Statement Explanation:

Traditional networks rely on VLANs and IP addresses for segmentation, but Free Mobility applies policies at the user level, allowing seamless access anywhere on the network.

Reference from Huawei HCIE-Datacom Documentation:

Huawei CloudCampus Solution Guide – Free Mobility and Policy Control

HCIE-Datacom Training Material – Identity-Based Networking

In MPLS VPN, packets are forwarded using two labels:

Outer label (Transport Label) – Used by the MPLS backbone for forwarding.

Inner label (VPN Label) – Used by the egress PE to identify the correct VPN instance.

Explanation of Correct Options:

✅ A. The egress PE sends the data packet to the correct VPN based on the inner label.

The inner label is assigned by the egress PE and determines the final destination VPN instance.

✅ B. The penultimate hop removes the outer label before forwarding the data packet to a peer egress PE.

Penultimate Hop Popping (PHP) occurs when the second-to-last router (P router) removes the outer MPLS label before forwarding to the egress PE.

This reduces the processing overhead on the egress PE.

✅ D. The penultimate-hop device receives a packet with an outer label.

The outer label is used to forward the packet across the MPLS backbone.

Before reaching the egress PE, the penultimate router still has the outer label and processes it.

Incorrect Option:

❌ C. The IP data packet received by the egress LSR is without labels.

This is incorrect because the inner label (VPN label) is still present when the packet reaches the egress PE.

Only the outer label is removed by PHP, not the inner VPN label.

Reference from Huawei HCIE-Datacom Documentation:

Huawei MPLS VPN Configuration Guide – Label Processing

HCIE-Datacom MPLS Traffic Engineering and PHP Mechanism

Huawei iMaster NCE-Campus MPLS VPN Implementation Guide

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.

The Time-To-Live (TTL) field in MPLS is essential for preventing infinite loops and enhancing security.

MPLS TTL Field Functionality:

It prevents packets from circulating indefinitely in the MPLS network.

It allows traceroute (tracert) to identify MPLS hops when TTL propagation is enabled.

Explanation of Correct Answers:✅ B. The processing of IP TTL copy hides the LSR in an MPLS domain, improving security.

If TTL propagation is disabled, MPLS routers do not decrease TTL, hiding internal LSRs from traceroute, enhancing security.

✅ C. MPLS provides two TTL processing modes:

Default Mode: The MPLS TTL copies the IP TTL value when an IP packet enters the MPLS network.

Uniform Mode: The ingress LER sets the MPLS TTL to 255, so it does not decrement.

✅ D. MPLS encapsulation in frame mode supports the TTL field, while cell mode does not.

Frame Mode (Ethernet, PPP, etc.) supports TTL.

Cell Mode (ATM/MPLS) does not support TTL.

Incorrect Answer Explanation:❌ A. If TTL copy is disabled, users can use the tracert function to view MPLS hops.

Wrong! If TTL propagation is disabled, tracert cannot see LSRs inside the MPLS core network.

Reference from Huawei HCIE-Datacom Documentation:

Huawei MPLS Technology Guide – TTL Field & Loop Prevention

HCIE-Datacom MPLS VPN Configuration Guide – Traceroute in MPLS Networks

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.”

WRED (Weighted Random Early Detection) helps prevent congestion by randomly discarding packets before buffers are full.

Drop Probability Behavior:

Below lower threshold = 0% drop (packets pass normally).

Between lower & upper threshold = Progressively increasing drop probability.

Above upper threshold = 100% drop (probability = 1).

✅ Reference: Huawei HCIE-Datacom Guide - WRED Mechanism

Intra-Area-Prefix-LSA (Type 9) is used in OSPFv3 to carry IPv6 prefix information for a router or network and is flooded within the area.

Link-LSA (Type 8) is only sent on the local link and is not flooded throughout the area.

Inter-Area-Prefix-LSA (Type 3) and Inter-Area-Router-LSA (Type 4) are also flooded within an area but originate from ABRs, typically for cross-area route advertisement.

That said, Intra-Area-Prefix-LSA is specifically flooded within an area, matching the context of the question directly.

Exact Extract - Huawei HCIE-Datacom OSPFv3 Module:

“Intra-Area-Prefix-LSAs are flooded within the area and advertise the IPv6 prefixes associated with router and network LSAs.”

Comprehensive and Detailed In-Depth Explanation:

The iMaster NCE-IP controller uses Telemetry to collect real-time device running status information efficiently and with low latency.

Telemetry (A): Enables continuous data streaming to the controller, including network performance and link state information.

Telnet (B): Used for manual device management and not suitable for automated data collection.

BGP-LS (C): Used for distributing link-state information, but not for real-time performance data collection.

IS-IS (D): An IGP protocol, not used for collecting device status.

In Huawei’s VXLAN implementation, the typical mapping between VNIs (VXLAN Network Identifiers) and BDs (Bridge Domains) is:

1:1 mapping — each VNI is uniquely associated with a single bridge domain.

This allows proper MAC learning and forwarding in the data plane for isolated tenant traffic.

Other mappings (N:1, 1:N, N:M) may be technically possible but not recommended or supported in most enterprise deployments.

Correct answer: B. 1:1

In MPLS Traffic Engineering (TE), Label Switched Paths (LSPs) can be established:

Statically: Manual configuration.

Dynamically: Typically via RSVP-TE.

Protocol roles:

RSVP-TE: Used to dynamically establish and signal TE LSPs → ✅

OSPF / IS-IS: Act as IGP protocols and provide TE-related link-state information (like bandwidth) but do not establish LSPs themselves → ❌

BGP: Used for route advertisement, not for LSP setup in MPLS TE → ❌

Correct answers: A, C, D