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

When VLAN-based MAC address flapping detection is configured, the following actions can be taken:

Alarm sending (generates logs or SNMP traps)

MAC address blocking (blocks specific flapping MAC addresses)

Interface blocking (shuts down or disables the interface temporarily)

Traffic filtering, however, is not an action option directly supported as a response to MAC flapping. Traffic filtering is part of ACL or QoS, not a built-in flapping response.

Exact Extract - Huawei Switching Configuration Guide – MAC Address Management:

“Actions that can be configured upon detection of MAC address flapping include sending alarms, blocking MAC addresses, and blocking interfaces. Traffic filtering is not supported as a direct action.”

InOSPFv3,Link-LSA (Type 8)is generated by a routerfor each of its interfacesto advertise:

Therouter's link-local addresson that interface.

TheIPv6 prefixesassociated with the interface.

Flags and options, such as router priority or loopback indicators.

From the output:

Link-LSA (Interface GigabitEthernet0/0/0)

Originating Router: 10.1.2.2

Link-Local Address: FE80::2E0:FCFF:FECD:4F79

Prefix: 2001:DB8:2345:23::/64

A. The link-local address of R2’s GE0/0/0 is FE80::2E0:FCFF:FECD:4F79→ This matches the Link-Local Address field in the LSA.✅

B. The IPv6 address prefix of R2’s GE0/0/0 is 2001:DB8:2345:23::/64→ This matches the Prefix field in the LSA.✅

C. This LSA indicates that R2 does not support external routes but can participate in IPv6 route calculation→❌Incorrect.

TheLink-LSAdoesnot provide any indicationabout external route capabilities.

It simply advertisesinterface-specific IPv6 and link-local info.

Whether R2 supports external routes depends onType 5 (External) or Type 7 (NSSA) LSAs, not Link-LSAs.

D. This LSA is generated by R2→ The Originating Router: 10.1.2.2 is R2’s router ID, so this LSA is definitely generated by R2.✅

Correct Answers:A, B, D

The Link-LSA in OSPFv3 contains:

The link-local address used by the originating router on the link.

A list of all IPv6 prefixes associated with the link.

Flags such as router priority and the Router-LSA options.

These LSAs are alwaysgenerated by the router itselfand arenot flooded beyond the link.

Comprehensive and Detailed In-Depth Explanation:

Telemetry in a narrow senserefers specifically to thedevice-side telemetryprocess, which includes the following key modules:

Data generation (A):The device collects and generates telemetry data, such as performance metrics or operational statistics.

Data push (B):The deviceactively pushes the collected datato the configured destination (such as a collector or management system) using a data streaming protocol.

Data source (C):The entity on the device that generates or provides themonitored data.

Data subscription (D)isnot part of the device-side telemetry; it is related to themanagement system side, where users subscribe to specific telemetry data streams.

Therefore, the correct answers areA, B, C.

InMPLS VPN, packets are forwarded usingtwo labels:

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

Inner label (VPN Label)– Used by theegress PEto 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.

Theinner label is assigned by the egress PEand 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 thesecond-to-last router(P router) removes the outer MPLS label before forwarding to theegress PE.

This reduces theprocessing overheadon the egress PE.

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

Theouter label is used to forward the packet across the MPLS backbone.

Before reaching the egress PE, thepenultimate router still has the outer labeland processes it.

Incorrect Option:

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

This isincorrectbecause theinner label (VPN label) is still presentwhen the packet reaches the egress PE.

Only theouter labelis 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

BGP EVPN Type 2 Route (MAC/IP Advertisement Route)

This route carriesMAC and IP address bindingsto inform remote VTEPs about locally learned endpoints.

Why Use arp collect host enable?

Collects ARP entriesof locally connected hosts.

EnablesBGP EVPN Type 2 route generationto distribute the learned ARP information.

Incorrect Answer Explanations:❌A. mac-address xxxx-xxxx-xxxx– Manually configures a MAC address butdoes not enable ARP collection for EVPN Type 2 routes.❌B. arp-proxy enable– Enables ARP Proxy butdoes not advertise ARP information using BGP EVPN.❌D. arp distribute-gateway enable– Used inDistributed Anycast Gateway (DAG) modebutnot for collecting host ARP data.

Reference from Huawei HCIE-Datacom Documentation:

Huawei VXLAN EVPN Configuration Guide – ARP Handling and EVPN Type 2 Routes

HCIE-Datacom Training Material – VTEP ARP Advertisement in VXLAN Networks

Let’s analyze the scenario and each statement carefully based on OSPF path selection and BGP behavior in Huawei routers.

✅ Option A: The preferred path is R1–R3–R4.

According to the OSPF cost values:

R1–R3–R4: Cost = 1 + 1 = 2

R1–R2–R4: Cost = 2 + 2 = 4

OSPF chooses the lowest-cost path to reach a destination. Therefore, R1 will prefer the R1–R3–R4 path to reach 172.20.1.4/32.

Huawei Datacom Reference:

"OSPF selects routes based on the shortest path calculated using link costs. The router always selects the path with the lowest cost."

(Source: HCIE-Datacom Study Guide v3.0 – OSPF Path Selection, Chapter 5)

✅ Option B: If the stub router on-startup command is run on R3, packet loss occurs during the power-off process of R3 but no packet loss occurs during the startup process of R3.

When R3 is powered off, OSPF needs to reconverge, which causes temporary packet loss.

When R3 starts up, it will advertise itself as a stub router using the stub-router on-startup command. This tells OSPF not to use R3 as a transit path during the startup period, thus preventing traffic blackholing.

Huawei Datacom Reference:

"stub-router on-startup command prevents a newly started router from being used as a transit node by OSPF, allowing routing to remain stable during convergence."

(Source: HCIE-Datacom Study Guide v3.0 – OSPF Stub Router Functionality, Chapter 6.2)

❌ Option C: The preferred path is R1–R2–R4.

This is incorrect because the OSPF path cost via R2 is higher (4) than the cost via R3 (2).

❌ Option D: Packet loss occurs during both the power-off and startup processes of R3.

Incorrect. As explained above, when the stub-router on-startup command is used, packet loss is avoided during startup, but still occurs during power-off since the alternate path requires convergence.

Huawei Open Programmability System (OPS) and Scripting Support

HuaweiOPS (Open Programmability System)enables network automation usingscript-based programmingfordevice management and configuration.

✅Python is the primary language integrated into Huawei OPS.

Python scripts can automate device configurations, monitoring, and troubleshooting.

OPS supports Python libraries for interacting with network APIs and CLI commands.

Used for Huawei CloudCampus, SDN, and Datacom devices.

IS-IS (Intermediate System to Intermediate System) protocolhas a limit on the size ofLink-State PDUs (LSPs).

Why Fragmentation?

LSPs contain routing and topology information.

If the LSPexceeds the maximum size, fragmentationallows the device to store and forward more routesby breaking them into smaller LSPs.

Key Point:IS-ISfragmentation is essentialin large-scale networks where routing tables grow beyond the default LSP size limit.

✅Reference:Huawei HCIE-Datacom Guide - IS-IS Protocol and Route Scaling

Understanding User Isolation in the Same VLAN

In a traditional VLAN,all devices within the same VLAN can communicateunless additional security policies are applied.To isolate users within the same VLAN, the following technologies can be used:

✅B. Port Isolation (Private VLAN or Layer 2 Isolation)

Prevents communication between ports within the same VLAN.

Common in enterprise and campus networksto improve security.

Example:Isolating guest users from employees within the same VLAN.

✅C. IPSG (IP Source Guard)

BlocksIP address spoofingwithin the same VLAN.

UsesDHCP snooping binding tableto verify whether a device is using anauthorized IP address.

✅D. Ethernet Port Security

Limits the number of MAC addressesallowed per port.

Preventsunauthorized devicesfrom communicating within the VLAN.

❌A. Super VLAN (Incorrect Choice)

Super VLANgroups multiple VLANs under a single Layer 3 gateway, but it doesnot provide isolationwithin the same VLAN.

Real-World Application:

Public Wi-Fi Networks:Ensures thatusers within the same VLAN cannot communicatewith each other.

Enterprise Security:Prevents unauthorized access or attacks withinshared VLANs.

✅Reference:Huawei HCIE-Datacom Guide – VLAN Security and User Isolation Technologies