Free Huawei H12-891_V1.0 Practice Exam with Questions & Answers | Set: 6

Understanding screen-length Command in Huawei Devices

????What Does screen-length Do?

Controlshow much output is displayed at a timeon the Huawei CLI.

By default, command output is paginated(split-screen display).

screen-length 0 temporarydisables the split-screen display, allowingcontinuous output without pauses.

Analysis of Each Option:

❌A. Performing automatic word wrap→Incorrect

This commanddoes not wrap long text lines, it controlsscreen pagination.

❌B. Performing split-screen display→Incorrect

This commanddisables split-screen display, not enables it.

✅C. Canceling split-screen display→Correct

This allowscontinuous command output without "Press Enter to continue" interruptions.

❌D. Canceling automatic word wrap→Incorrect

Word wrap behavior isnot controlled by screen-length.

Real-World Application:

Automated Network Monitoring:Used inPython scriptsforuninterrupted CLI output collection.

Log Analysis:Helps inextracting large command outputsfortroubleshooting.

✅Reference:Huawei HCIE-Datacom Guide – CLI Configuration and Automation with Paramiko

Comprehensive and Detailed In-Depth Explanation:

In theHuawei iMaster NCE-Campussolution, when using athird-party Portal authentication application, the following process occurs:

After the Wi-Fi user connects to the network, any attempt toaccess a website for the first timetriggersHTTP redirection.

The user isredirected to the login pageprovided by the third-party authentication application.

This mechanism ensures that the userauthenticatesbefore accessing external resources.

The redirection behavior is consistent withcaptive portal functionality, which is standard for user authentication on Wi-Fi networks.

Therefore, the statement isTRUE.

Comprehensive and Detailed In-Depth Explanation:

In theCloudCampus public cloud scenario, when devices are deployed through theHuawei registration query center, there isno need to configure DHCP Option 148on the campus network’s DHCP server.

Theregistration query centerautomatically provides thecontroller IP addressto the devices during the registration process.

DHCP Option 148is typically used to provide theiMaster NCE-Campus addressin on-premises or private cloud scenarios.

In thepublic cloud scenario, the devices obtain this information directly from the Huawei cloud platform, makingOption 148 unnecessary.

Understanding BGP Link State (BGP-LS)

????What is BGP-LS?

BGP-LS (BGP Link-State)is anextension of BGPthat allows routers to exchangenetwork topology informationviaLink-State NLRI.

HelpsSDN controllers and path computation elements (PCEs)makeintelligent routing decisions.

????What Does BGP-LS Advertise?

✅Node Information– Router IDs, Loopbacks

✅Link Information– Bandwidth, Delay, Cost

✅Prefix Information– Network Subnets

✅Topology Information– Full network graph

Why is the Answer TRUE?

✅BGP-LS introduces a new NLRI formatfor advertising link-state information.

✅NLRI (Network Layer Reachability Information) is used to distribute topology datato SDN controllers.

✅It improves path optimization by enabling centralized traffic engineering decisions.

Real-World Application:

SDN-Based Traffic Engineering:Used inSegment Routing (SR)networks for centralizedpath selection.

MPLS TE (Traffic Engineering):Optimizes network paths dynamically based onreal-time link-state data.

✅Reference:Huawei HCIE-Datacom Guide – BGP Link-State (BGP-LS) Fundamentals

Understanding SR-MPLS Prefix and Adjacency Segments

????What Are Prefix Segments?

Globally uniquelabels assigned to network prefixes.

Advertised viaIGP (OSPF, IS-IS) with SRGB (Segment Routing Global Block).

????What Are Adjacency Segments?

Locally significant labelsassigned to direct router adjacencies.

Not globally visible—only used within a local router’sLFIB (Label Forwarding Information Base).

Why is the Answer FALSE?

❌Prefix Segments are globally unique, but Adjacency Segments are only locally significant.

❌Adjacency Segments are not distributed globally through IGP.

✅Only Prefix Segments use globally advertised SRGB labels.

Real-World Application:

Segment Routing Traffic Engineering (SR-TE):Usesprefix segments for global routingandadjacency segments for local path steering.

5G Core Networks:UsesSR-MPLS with Prefix SIDs for scalable path selection.

✅Reference:Huawei HCIE-Datacom Guide – SR-MPLS Prefix & Adjacency Segments

In BGP EVPN configuration forVXLAN-based networks, Huawei uses the command:

[bgp] advertise l2vpn evpn

This command enables the BGP process toadvertise routes from a VPN instance into the EVPN (L2VPN) address family, which is used for VXLAN control-plane operations like MAC/IP advertisement.

Option A (advertise irbvfi)— invalid command.

Option B (advertise vpnv4)— used for MPLS VPNs, not EVPN.

Option C (advertise irb)— not a recognized Huawei command.

Option Dis the correct and officially used command.

Correct answer: D. advertise l2vpn evpn

Comprehensive and Detailed In-Depth Explanation:

TheStrict Priority (SP) scheduling algorithmalways gives preference to high-priority queues.

A:Correct. SP scheduling may lead toqueue starvationbecause low-priority queues might never get serviced if high-priority traffic is constant.

B:Correct. SP always schedules thehighest-priority queue first.

C:Correct. Among multiple low-priority queues, if SP is combined with FIFO (First In, First Out), packets that arrive first are forwarded first.

D:Incorrect. The SP algorithmdoes not guarantee minimum bandwidthfor lower-priority queues. It prioritizes high-priority queues regardless of bandwidth configuration, which can lead to starvation of lower-priority traffic. To ensure minimum bandwidth, aWeighted Fair Queuing (WFQ)orCBWFQ (Class-Based Weighted Fair Queuing)algorithm would be more suitable.

NETCONF definesdatastoresto manage device configurations:

running: Active configuration in use

candidate: Staging area for changes before applying

startup: Configuration loaded on reboot

NETCONF operations:

: Applies changes fromcandidate → running→✅

: Deletes a specified datastore (e.g., startup) →✅

: Validates syntax/logic in thecandidate datastore→✅

Statement D is incorrect: never submits config from startup to running— that’s handled automatically at boot time, not through NETCONF commands.

Correct answer: D

Comprehensive and Detailed Explanation:

The IS-IS peer output shows:

IPv4 Peer Address:10.1.34.1

IPv6 Peer Address:FE80::2E0:FCFF:FE98:2576

MT IDs (Multi-Topology) Supported:0 (IPv4), 2 (IPv6)

Sinceboth IPv4 and IPv6 peer addressesare listed, it confirms thatboth IPv4 and IPv6 IS-IS neighbor relationships are establishedbetweenR4 and ee8c.a0c2.baf3.

????Reference:Huawei HCIE Datacom – IS-IS Multi-Topology Support

VRRP (Virtual Router Redundancy Protocol) and Flapping

VRRP ensuresgateway redundancyby allowing multiple routers to work together as avirtual router.Flappingoccurs when themaster and backup routers frequently switch roles.

Causes of VRRP Flapping:

✅A. Too small interval between Advertisement packet transmissions–Can cause flapping

If theAdvertisement interval is too short, frequent VRRP state changes can occur.

✅C. Packet loss on an interface of the backup device–Can cause flapping

If thebackup router loses VRRP packets, it might assume themaster is downand initiate an election.

✅D. Flapping on the link transmitting VRRP Advertisement packets–Can cause flapping

If the link used for VRRPexperiences instability, packets may be lost, triggering VRRP role changes.

Incorrect Answer Explanation:

❌B. Inconsistent preemption delay settings – Does NOT cause VRRP flapping

Preemption delay only affectswhen a router takes over as masterafter recovering from a failure.

It doesnot directly cause flappingbecause the role change happens onlyafter a delay, preventing frequent transitions.

Reference from Huawei HCIE-Datacom Documentation:

Huawei VRRP Configuration Guide – Preventing VRRP Flapping

HCIE-Datacom Study Material – VRRP Timers and Stability